Physiology E3 BRS

A. Hyperglycemia and diuresis Selective loss of pancreatic β cells results in type 1 diabetes mellitus (see Clinical Application 33.1). Symptoms include high blood glucose (hyperglycemia) that can spill over into the urine and cause an increase in urinary water loss (diuresis).

A 10-year-old boy with an autoimmune disease that destroyed his pancreatic β cells is most likely to exhibit which of the following signs and symptoms? A. Hyperglycemia and diuresis B. Hyperkalemia C. Enhanced protein storage in muscle D. Decreased circulating fatty acid levels E. Enhanced glucose uptake by adipocytes

A. Reverse T3 has little biological effect. Reverse T3 has no biological effect. Individuals with anorexia nervosa often have an increased rT3 level and a lower T3 level, reflecting a lower metabolism rate as compensation for the markedly decreased caloric intake. The fact that her TSH is in the normal range makes it difficult to make a diagnosis of hypothyroidism.

A 15-year-old adolescent is suspected of having anorexia nervosa. Thyroid function tests are also drawn. Her TSH is in the normal range, but the rT3 level is elevated. Which of the following is the most accurate statement regarding her status? A. Reverse T3 has little biological effect. B. This patient probably has T3 thyroiditis. C. The free rT3 would be the next step to assess possible hyperthyroidism. D. This patient probably has hypothyroidism

E. Dihydrotestosterone 5α-Reductase is an enzyme normally found in several tissues that converts testosterone to dihydrotestosterone (DHT). A 5α-reductase deficiency would, thus, result in reduced DHT levels. DHT mediates many androgen effects, so individuals with a 5α-reductase deficiency do not express many male secondary sex characteristics until puberty, when testosterone levels dramatically increase

A 16-year-old suffers from a 5α-reductase deficiency. This individual was raised as a girl, but, at puberty, male secondary sex characteristics emerged, and male genital growth occurred. Levels of which of the following steroids are most likely to be reduced as a result of this deficiency until overwhelmed during puberty? A. Estradiol B. Estrone C. Progesterone D. Androstenedione E. Dihydrotestosterone

C. Elevated serum testosterone The elevated serum testosterone is due to lack of androgen receptors on the anterior pituitary (which normally would mediate negative feedback by testosterone).

A 16-year-old, seemingly normal female is diagnosed with androgen insensitivity disorder. She has never had a menstrual cycle and is found to have a blind-ending vagina; no uterus, cervix, or ovaries; a 46 XY genotype; and intra-abdominal testes. Her serum testosterone is elevated. Which of the following characteristics is caused by lack of androgen receptors? A. 46 XY genotype B. Testes C. Elevated serum testosterone D. Lack of uterus and cervix E. Lack of menstrual cycles

C. Polycystic ovarian disease The history of hair growth and irregular menstrual cycles points to polycystic ovarian disease, the most common cause of androgen excess and hirsutism. Patients exhibit obesity, oligomenorrhea, hirsutism, acne, and infertility. The distribution of abnormal hair growth reflects the severity of androgen excess. Congenital adrenal hyperplasia (choice A) can be excluded because it is characterized by increased 17-hydroxyprogesterone levels. Sertoli-Leydig cell tumors (choice B) are ovarian neoplasms that secrete testosterone. They occur in women between the ages of 21 and 40 years. Patients with these tumors abruptly cease having menses and exhibit extensive body hair as well as temporal hair recession, clitoral enlargement, deepening of the voice, and an ovarian mass. Cushing syndrome (choice D) in unlikely because free cortisol levels were normal. Constitutional hirsutism (choice E) is hirsutism with no known cause. Women with this condition have regular menstrual cycles

A 19-year-old unmarried woman complains that she is "too hairy." She has a history of severe irregular menstrual cycles; worsening acne; and hair growth on the face, breasts, and lower abdomen. She is sexually active, uses condoms for contraception, and is otherwise well. Laboratory values revealed normal levels of testosterone, cortisol, 17-hydroxyprogesterone, and DHEA but elevated LH levels. She is, however, depressed about the new hair growth. Which of the following is the most likely cause for these symptoms? A. Congential adrenal hyperplasia B. Sertoli-Leydig cell tumor of the ovary C. Polycystic ovarian disease D. Cushing syndrome E. Constitutional hirsutism

B. Ketone levels The patient is exhibiting signs and symptoms of acute hyperglycemia. In patients with diabetes, ketone bodies are elevated because of the inability to rely on glucose as the primary energy substrate. Rapid breathing also indicates ketones, as this is a respiratory response to a metabolic acidosis (ketoacidosis).

A 20-year-old man has sudden onset of weakness, dizziness, altered vision, and rapid breathing. He reports frequent urination and insatiable thirst. A urinalysis is positive for glucose. In this case, which blood values are most likely to be elevated? A. Fructose levels B. Ketone levels C. High-density lipoprotein levels D. Hormone-sensitive lipase levels E. Hemoglobin A1c levels

A. Estradiol Gonadotropes, which are located in the anterior pituitary, normally respond to a stimulating hormone by releasing both FSH and LH. FSH stimulates aromatase within granulosa cells, which converts androgens from surrounding theca cells into estrogens, including estradiol.

A 20-year-old woman who was administered a gonadotrope-stimulating drug responded with an increase in plasma luteinizing hormone (LH) levels, but follicle-stimulating hormone (FSH) levels remained low. Levels of which of the following hormones would also be expected to remain unaffected by such a drug? A. Estradiol B. Progesterone C. Androstenedione D. Testosterone E. DHEA

A. Lipolysis in adipocytes Glucagon's principal function is to mobilize energy substrates and release them to the circulation for use by cells (see 33·III·C·2). Its actions include stimulating hormone-sensitive lipase in adipocytes. The lipase breaks down triacylglycerols into free fatty acids and glycerol (lipolysis), which are then released into the circulation.

A 22-year-old woman is participating in a drug study affecting pancreatic hormones. If the test drug greatly elevates glucagon levels while having no effect on insulin release, which of the following processes are most likely to increase? A. Lipolysis in adipocytes B. Glycolysis in skeletal and cardiac muscle C. Gluconeogenesis in neurons D. Glucose uptake in hepatocytes E. Ketone uptake in neurons

A. Be somewhat taller than average Because testosterone plays a major role in causing epiphyseal closure, growth continues past the normal age of puberty. Although body hair is less abundant, pubic and axillary hair is present as a result of adrenocortical androgen secretion. In contrast, male pattern baldness, which is attributed to the actions of androgens, will not occur. Because androgens are required for growth of the larynx and vocal cords, the voice deepening associated with puberty will not take place.

A 24-year-old male has been lacking the production of testosterone since early childhood and has not been treated. He will likely exhibit which of the following signs? A. Be somewhat taller than average B. Have a deep voice C. Have abundant chest hair D. Have no pubic or axillary hair E. Undergo premature baldness

C. Nephrogenic diabetes insipidus due to lithium treatment Lithium treatment decreases the effects of ADH on the kidney, resulting in polyuria and polydipsia from volume depletion. SIADH (choice A) is associated with inappropriate ADH secretion, leading to hyponatremia and defective excretion of a water load, which is contrary to the symptoms described in the case. Hyperglycemia with osmotic diuresis (choice B) causes a loss of water that results in increased ADH release as the hypothalamus senses hypovolemia and secretes ADH to retain water to maintain intravascular volume. Because the patient has a long history of diabetes, symptoms would not develop in 1-week's time. In a patient with psychogenic polydipsia (choice D), the urine osmolality would increase more than the plasma osmolality after the water restriction test, indicating that anti diuresis is occurring. Central diabetes insipidus with panhypopituitarism (choice E) is not correct because a person with panhypopituitarism would exhibit multiple pituitary deficiencies, including growth failure and hypogonadism, which were not mentioned in this case.

A 30-year-old man has a 1-week history of increased thirst (polydipsia) and increased urine volumes (polyuria). The results of a water deprivation test reveal increased plasma osmolality (>300 mOsm/kg) and elevated urine osmolality (>120 mOsm/kg). He is currently receiving treatment for non-insulin-dependent diabetes mellitus (type II) as well as for bipolar disorder. Which of the following is the most likely diagnosis? A. SIADH due to oral hypoglycemic agents B. Hyperglycemia with osmotic diuresis C. Nephrogenic diabetes insipidus due to lithium treatment D. Polydipsia E. Central diabetes insipidus caused by panhypopituitarism

B. Excess PRL secretion Galactorrhea is commonly associated with pituitary tumors secreting excess PRL. Prolactin is important in maintaining milk production in the breast after birth. Insufficient LHRH secretion would result in low levels of PRL, which would not stimulate galactorrhea. Galactorrhea is diagnosed if present longer than 6 months postpartum in a nonnursing mother. The combination of both galactorrhea and amenorrhea is diagnostic of PRL-secreting pituitary tumor. TSH generally has little effect on PRL secretion. GH has lactogenic activity when high not low. Hypothalamic dopamine is an inhibitor of PRL release.

A 30-year-old woman completed a routine pregnancy with the uncomplicated delivery of a normal-sized baby girl 6 months ago. The woman is currently experiencing galactorrhea (persistent discharge of milklike secretions from the breast) and has not yet resumed regular menstrual periods. The baby had been bottle-fed since birth. What is the most likely explanation of the galactorrhea? A. Normal postpartum response B. Excess PRL secretion C. Insufficient TSH secretion D. Reduced GH secretion E. Increased dopamine synthesis in the hypothalamus

A. Muscle weakness Corticosteroids normally prepare the body for stress by mobilizing substrates, such as glucose and free fatty acids (see 34·II·D·1). This is accomplished in part through skeletal muscle protein catabolism, so prolonged cortisol administration can cause muscle weakness.

A 32-year-old man with suspected adrenocortical insufficiency is being treated with a synthetic cortisol (hydrocortisone). High doses improve his symptoms. If this dosing regimen is continued for a prolonged period of time, what is the most likely result? A. Muscle weakness B. Bone deposition and collagen formation C. Virilization D. β-Adrenergic receptor desensitization E. Adrenal gland hypertrophy

A. Graves disease In most cases of Graves hyperthyroidism, an IgG antibody to TSH receptors known to stimulate thyroid cells is present in the patient's serum. Multinodular toxic goiter (choice B) occurs primarily in elderly patients. Hypothyroidism of hypothalamic origin (choice C); primary hypothyroidism (choice D); and myxedema, which is prolonged hypothyroidism (choice E), are incorrect because the case describes hyperthyroidism, not hypothyroidism

A 32-year-old previously healthy woman has a 1-year history of palpitations, sweating, heat intolerance, and intermittent diarrhea. She has lost 12 lbdespite a good appetite. Her niece had neonatal hypothyroidism. Physical examination reveals an anxious woman with a pulse rate of 120/min and blood pressure of 120/80 mm Hg. She exhibits a fine tremor of the hands and has moist, warm palms. Laboratory investigation shows elevated free T3 and T4 as well as increased plasma TSH levels. Which of the following is the most likely diagnosis? A. Graves disease B. Multinodular toxic goiter C. Hypothyroidism of hypothalamic origin D. Primary hypothyroidism E. Myxedema

C. It binds onto a cytoplasmic receptor, and the hormone-receptor complex diffuses to the nucleus to affect transcription. Thyroxine behaves similarly to steroid hormones in that it binds onto cytoplasmic receptors, and the hormone-receptor complex then diffuses to the nucleus to affect the transcription of DNA and ultimately protein synthesis. Most protein hormones bind to surface membrane receptors; thyroid hormone is an exception.

A 33-year-old chemist takes L-thyroxine (Synthroid) 1 μg orally each day. He asks how the thyroxine works on a cellular level. Which of the following is the best explanation? A. It binds onto membrane surface receptor and activates protein synthesis. B. It binds onto membrane surface receptor and activates a secondary messenger. C. It binds onto a cytoplasmic receptor, and the hormone-receptor complex diffuses to the nucleus to affect transcription. D. It has a direct effect on the hypothalamic nuclei affecting metabolism

C. Normal thyroid status This patient has an elevated total thyroxine level because of increased TBG. However, the free (active) thyroxine is normal, and the TSH is in the normal range, both of which indicate a normal euthyroid state. Women who are pregnant or on an oral contraceptive agent may develop an increased TBG; hence, free T4 or TSH levels are better tests to assess thyroid status.

A 33-year-old woman is noted by her physician to have some fatigue and some coarse skin. Her only medication is an oral contraceptive agent. The following laboratories have been returned: TSH 1.0 mU/L (0.35-6.0 mU/L) Free thyroxine 1.0 ng/dL (0.8-2.7 ng/dL) Total thyroxine 13.0 μg/dL (4.5-12.0 μg/dL) Thyroid-binding globulin (TBG) 55 ng/mL (15-34 mg/L) Which of the following is the most likely diagnosis? A. Hyperthyroidism B. Hypothyroidism C. Normal thyroid status D. Transient hyperthyroidism

D. Primary hypothyroidism Laboratory test results (low thyroid hormone and elevated serum TSH levels) along with physical findings of pale, cold, dry skin are consistent with primary hypothyroidism. Graves disease (choice A) is an autoimmune disorder characterized by production of antibodies to the TSH receptor. Hyperthyroidism results when thyroid stimulating immunoglobulins act as agonists on the TSH receptor, stimulating thyroid hormone synthesis and secretion. Multinodular toxic goiter (choice B) is most commonly seen in the elderly and results in hyperthyroidism, not hypothyroidism. Hypothyroidism of hypothalamic origin (choice C) is an uncommon cause of hypothyroidism and is due to central (pituitary/hypothalamic) defects that result in decreased TSH levels, not increased TSH levels. Diffuse toxic goiter (choice E) is another name for Graves disease and is characterized by hyperthyroidism due to an overactive thyroid gland, not hypothyroidism.

A 34-year-old female patient has an 8-year history of menorrhagia (abnormal bleeding) and anemia. Symptoms of tiredness and inability to concentrate caused her to lose her job. She also complains of cold intolerance, constipation, and weight gain. Upon examination her skin is pale, cold, dry, and scaly. Laboratory results indicate low plasma T4 levels and elevated plasma TSH levels. Which of the following is the most likely diagnosis? A. Graves disease B. Multinodular toxic goiter C. Hypothyroidism of hypothalamic origin D. Primary hypothyroidism E. Diffuse toxic goiter

D. Muscle spasms and tetany Removal of the parathyroid glands may lead to hypocalcemia. Symptoms include nerve paresthesias, muscle spasms, and tetany. A physical sign is the Trousseau sign, the development of carpal spasm when the blood pressure cuff is inflated for about 2 to 3 minutes. The Chvostek sign is twitching of facial muscle when the facial nerve is percussed lightly anterior to the ear. Severe hypocalcemia can lead to seizures, laryngospasm, and lethargy. The other answers refer to symptoms or signs of hypercalcemia.

A 35-year-old woman undergoes a thyroidectomy for papillary serous thyroid cancer. The surgeon suspects that the parathyroid glands have been removed. Which of the following findings is most likely to be seen in the patient 1 week postoperatively? A. Coma B. Constipation C. Esophagitis D. Muscle spasms and tetany

C. inhibits prolactin release from the anterior pituitary

A 38-year-old man who has galactorrhea is found to have a prolactinoma. His physician treats him with bromocriptine, which eliminates the galactorrhea. The basis for the therapeutic action of bromocriptine is that it A. antagonizes the action of prolactin on the breast B. enhances the action of prolactin on the breast C. inhibits prolactin release from the anterior pituitary D. inhibits prolactin release from the hypothalamus E. enhances the action of dopamine on the anterior pituitary

D. blood pH

A 39-year-old man with untreated diabetes mellitus type I is brought to the emergency room. An injection of insulin would be expected to cause an increase in his A. urine glucose concentration B. blood glucose concentration C. blood K+ concentration D. blood pH E. breathing rate

B. 46 XY

A 4 year old girl presents with bilateral inguinal masses, thought to be hernias, but these were found to be testes in the inguinal canals. The karyotype would most likely be: A. 46 XX B. 46 XY C. 47 XXY D. 47 XYY

D. hypoparathyroidism after thyroid surgery Low blood [Ca2+] and high blood [phosphate] are consistent with hypoparathyroidism. Lack of parathyroid hormone (PTH) decreases bone resorption, decreases renal reabsorption of Ca2+, and increases renal reabsorption of phosphate (causing low urinary phosphate).

A 41-year-old woman has hypocalcemia, hyperphosphatemia, and decreased urinary phosphate excretion. Injection of parathyroid hormone (PTH) causes an increase in urinary cyclic adenosine monophosphate (cAMP). The most likely diagnosis is A. primary hyperparathyroidism B. vitamin D intoxication C. vitamin D deficiency D. hypoparathyroidism after thyroid surgery E. pseudohypoparathyroidism

D. Hypernatremia The anterior pituitary secretes thyroid-stimulating hormone, GH, adrenocorticotropic hormone, prolactin, follicle-stimulating hormone, and luteinizing hormone, whereas the posterior pituitary secretes oxytocin and antidiuretic hormone (ADH). Lack of ADH would lead to the inability to resorb free water, leading to hypernatremia.

A 45-year-old woman has a cerebrovascular accident that causes necrosis of the posterior pituitary. Which of the following effects is most likely to be seen? A. Inability to lactate B. Hypothyroidism C. Hypoglycemia D. Hypernatremia

C. Increases iodide uptake Thyroid follicular cells are epithelial cells specialized for thyroid hormone synthesis and release (see 35·II·A). TSH regulates many steps in the synthetic pathway, including iodide uptake by Na+-I− symporters (NIS, or cotransporters). TSH upregulates NIS.

A 45-year-old woman suffers from symptoms associated with hypothyroidism. A blood sample reveals that thyroid-stimulating hormone (TSH) levels are above normal. Which of the following statements best describes its action on thyroid follicular cells? A. Inhibits pendrin insertion B. Inhibits growth C. Increases iodide uptake D. Increases blood flow E. Increases thyroxine-binding globulin synthesis

A. Increased FSH The subject is experiencing early menopause, which is characterized by increased FSH trying to stimulate follicular development and maturation. Decreased LH (choice B), increased bone density (choice C), decreased total cholesterol (choice D), and increased estradiol levels (choice E) are not characteristic of menopause. Rather, the opposite findings are associated with menopause.

A 46-year-old woman complains of increasing irritability, hot flashes, and an increasingly irregular menstrual cycle over the past 12 months. She has had three uncomplicated pregnancies and has no other problems other than varicose veins. Which of the following findings would be expected? A. Increased FSH B. Decreased LH C. Increased bone density D. Decreased total cholesterol E. Increased estradiol levels

C. primary overproduction of ACTH (Cushing disease) This woman has the classic symptoms of a primary elevation of adrenocorticotropic hormone (ACTH) (Cushing disease). Elevation of ACTH stimulates overproduction of glucocorticoids and androgens. Treatment with pharmacologic doses of glucocorticoids would produce similar symptoms, except that circulating levels of ACTH would be low because of negative feedback suppression at both the hypothalamic (corticotropin-releasing hormone [CRH]) and anterior pituitary (ACTH) levels.

A 46-year-old woman has hirsutism, hyperglycemia, obesity, muscle wasting, and increased circulating levels of adrenocorticotropic hormone (ACTH). The most likely cause of her symptoms is A. primary adrenocortical insufficiency (Addison disease) B. pheochromocytoma C. primary overproduction of ACTH (Cushing disease) D. treatment with exogenous glucocorticoids E. hypophysectomy

D. Pituitary Cushing disease due to a pituitary adenoma Pituitary Cushing disease is due to a benign pituitary adenoma that secretes excessive ACTH, producing clinical symptoms of excessive cortisol levels.

A 48-year-old farmer has a 10-month history of muscle weakness, easy bruising, backache, headache, and depression. He is a lifelong nonsmoker who has previously been healthy. His only medication is a nonsteroidal anti-inflammatory agent taken for rib pain. Upon examination, truncal obesity with a "buffalo hump," thin skin with easy bruising, and a blood pressure of 180/100 mm Hg are noted. Laboratory studies reveal elevated free cortisol with an absence of a circadian rhythm. A high-dose dexamethasone test suppressed AM cortisol levels to less than 50% of basal values.Which of the following is the most likely diagnosis? A. Addison disease due to autoimmune destruction of the adrenal B. Ectopic Cushing disease due to small cell carcinoma of the lung C. 17-α-Hydroxylase deficiency due to a congenital defect D. Pituitary Cushing disease due to a pituitary adenoma E. Primary hyperaldosteronism from adrenal adenoma

E. Reduced renal activity of 1 α-hydroxylase activity (which converts the inactive form of vitamin D to the active form) The key observation is that the patient has renal insufficiency or is in the early stages of chronic renal failure. This reduces the levels of 1 α-hydroxylase in the proximal tubule cells, thereby reducing the conversion of 25-hydroxyvitamin D, the inactive form of vitamin D, to 1,25-dihydroxyvitamin D, the most active form.

A 50-year-old individual is admitted to the emergency room with a fractured tibia. The fracture occurred while this person was lifting light boxes. Bone scans of the spine and hip reveal low bone density. Laboratory tests show low plasma calcium, elevated PTH levels, and low vitamin D levels. The patient indicates that she is on a balanced diet with sufficient fruits and vegetables. However, the patient's plasma creatinine and blood urea nitrogen (BUN) levels are elevated markedly. Which of the following is the most likely reason for the hypocalcemia and reduced bone mass? A. Excessive urinary excretion of calcium B. Impaired secretion of calcitonin C. Low dietary calcium D. A parathyroid gland tumor generating excessive amounts of PTH E. Reduced renal activity of 1 α-hydroxylase activity (which converts the inactive form of vitamin D to the active form)

C. GH deficiency Growth hormone deficiency in adults is characterized by decreased muscle strength and exercise intolerance, and a reduced sense of well-being (including effects on libido). Lean body mass (muscle) is lost, and excess body fat deposition occurs in the abdominal region. GH replacement can reverse these effects.

A 50-year-old man complains of decreased muscle strength, libido, and exercise intolerance. Examination reveals a 10% reduction in lean body mass and an increase in body fat, primarily localized to the abdominal region. Thyroid hormone levels are normal. Which diagnosis is most consistent with these symptoms? A. Glucocorticoid deficiency B. Addison disease C. GH deficiency D. PRL deficiency E. Acromegaly

B. Oxidation Oxidation is the first step of thyroid hormone formation affected (see 35·II·A). In this step, iodide is oxidized as soon as it crosses the apical membrane into the colloid.

A 55-year-old woman with hyperthyroidism is given propylthiouracil (PTU), which inhibits thyroid peroxidase. Based on PTU's mechanism of action, which of the following stages of thyroid formation would be the first affected? A. Trapping B. Oxidation C. Iodination D. Conjugation E. Proteolysis

E. iodide (I−)

A 61-year-old woman with hyperthyroidism is treated with propylthiouracil. The drug reduces the synthesis of thyroid hormones because it inhibits oxidation of A. triiodothyronine (T3) B. thyroxine (T4) C. diiodotyrosine (DIT) D. thyroid-stimulating hormone (TSH) E. iodide (I−)

C. Increased serum ACTH, increased serum cortisol, and increased serum insulin

A 7-year-old boy comes to the pediatric endocrine unit for evaluation of excess body weight. Review of his growth charts indicates substantial weight gain over the previous 3 years but little increase in height. To differentiate between the development of obesity and Cushing syndrome, blood and urine samples are taken. Which of the following would be most diagnostic of Cushing disease? A. Increased serum ACTH, decreased serum cortisol, and increased urinary free cortisol B. Decreased serum ACTH, increased serum cortisol, and increased serum insulin C. Increased serum ACTH, increased serum cortisol, and increased serum insulin D. Increased serum ACTH, decreased serum cortisol, and decreased serum insulin E. Increased serum ACTH, decreased serum cortisol, and decreased urinary free cortisol F. Decreased serum ACTH, decreased serum cortisol, and increased serum insulin

D. nephrogenic diabetes insipidus

A 76-year-old man with lung cancer is lethargic and excreting large volumes of urine. He is thirsty and drinks water almost constantly. Laboratory values reveal an elevated serum Ca2+ concentration of 18 mg/dL, elevated serum osmolarity of 310 mOsm/L, and urine osmolarity of 90 mOsm/L. Administration of an ADH analogue does not change his serum or urine osmolarity. The cause of the patient's excess urine volume is A. dehydration B. syndrome of inappropriate ADH C. central diabetes insipidus D. nephrogenic diabetes insipidus

D. increased because the elevated serum osmolarity has stimulated ADH secretion The man is excreting large volumes of dilute urine, which has raised his serum osmolarity and made him very thirsty. The increase in serum osmolarity would then cause an increase in serum ADH levels.

A 76-year-old man with lung cancer is lethargic and excreting large volumes of urine. He is thirsty and drinks water almost constantly. Laboratory values reveal an elevated serum Ca2+ concentration of 18 mg/dL, elevated serum osmolarity of 310 mOsm/L, and urine osmolarity of 90 mOsm/L. Administration of an ADH analogue does not change his serum or urine osmolarity. The man's serum ADH level is A. decreased because excess water-drinking has suppressed ADH secretion B. decreased because his posterior pituitary is not secreting ADH C. normal D. increased because the elevated serum osmolarity has stimulated ADH secretion E. increased because his extreme thirst has directly stimulated ADH secretion

E. pamidronate plus furosemide The man's nephrogenic diabetes insipidus is caused by hypercalcemia secondary to increased PTH-rp secreted by his lung tumor. PTH-rp has all of the actions of PTH, including increased bone resorption, increased renal Ca2+ reabsorption, and decreased renal phosphate reabsorption; all of these actions lead to increased serum Ca2+ concentration.

A 76-year-old man with lung cancer is lethargic and excreting large volumes of urine. He is thirsty and drinks water almost constantly. Laboratory values reveal an elevated serum Ca2+ concentration of 18 mg/dL, elevated serum osmolarity of 310 mOsm/L, and urine osmolarity of 90 mOsm/L. Administration of an ADH analogue does not change his serum or urine osmolarity. The most appropriate treatment is A. ADH antagonist B. ADH analogue C. PTH analogue D. half-normal saline E. pamidronate plus furosemide

C. Mental ability would be impaired, body growth rate would be slowed, and thyroid gland size would be smaller than normal. Thyroid hormones are important for normal development of the CNS and for body growth. TSH stimulates the synthesis and release of thyroid hormones as well as the growth of the thyroid gland. In a disorder in which the thyroid gland does not respond to TSH, thyroid hormone production would be decreased, resulting in poor development of the CNS and poor body growth. TSH would also not be able to stimulate the growth of the thyroid, resulting in a small gland.

A child is born with a rare disorder in which the thyroid gland does not respond to TSH. What would be the predicted effects on mental ability, body growth rate, and thyroid gland size when the child reaches 6 years of age? A. Mental ability would be impaired, body growth rate would be slowed, and thyroid gland size would be larger than normal. B. Mental ability would be unaffected, body growth rate would be slowed, and thyroid gland size would be smaller than normal. C. Mental ability would be impaired, body growth rate would be slowed, and thyroid gland size would be smaller than normal. D. Mental ability would be unaffected, body growth rate would be unaffected, and thyroid gland size would be smaller than normal. E. Mental ability would be impaired, body growth rate would be slowed, and thyroid gland size would be normal. F. Mental ability would be unaffected, body growth rate would be unaffected, and thyroid gland size would be unaffected.

A. Neurophysin Neurophysin is the other product generated when the prohormone for AVP or oxytocin is cleaved. A decrease in blood volume would result in the release of AVP and neurophysin from magnocellular neurons. The hormones oxytocin, β-lipotropin, ACTH, and somatostatin are not involved in the regulation of blood volume.

A decrease in blood volume would result in an increase in the secretion of: A. Neurophysin B. Oxytocin C. β-lipotropin D. Somatostatin E. ACTH F. POMC

F. Glucocorticoids should be increased to compensate for the increased stress associated with surgery. Patients on long-term glucocorticoid therapy should have the dose increased prior to undergoing surgery to minimize the effects of surgical stress. These patients cannot mount their own stress response because of the lack of adrenal cortisol release. Glucocorticoid-induced hypoglycemia or interactions with anesthetics are not likely, and these concerns would be secondary to stimulating the response to surgical stress. Glucocorticoids inhibit ACTH release and the immune response. Glucocorticoids increase the response of the vasculature to catecholamines.

A patient receiving long-term glucocorticoid therapy plans to undergo hip replacement surgery. What would the physician recommend prior to surgery and why? A. Glucocorticoids should be decreased to prevent serious hypoglycemia during recovery. B. Glucocorticoids should be increased to stimulate immune function and prevent possible infection. C. Glucocorticoids should be decreased to minimize potential interactions with anesthetics. D. Glucocorticoids should be increased to stimulate ACTH secretion during surgery to promote wound healing. E. Glucocorticoids should be decreased to prevent inadequate vascular response to catecholamines during recovery. F. Glucocorticoids should be increased to compensate for the increased stress associated with surgery.

C. Day 15 The corpus luteum has an inherit life span of 14 days, resulting in a 14-day luteal phase. Ovulation occurs just before the luteal phase. Subtracting 14 days from the patient's menstrual duration (29 days) gives an approximate day of ovulation (day 15).

A patient with a 29-day menstrual cycle probably ovulated on which of the following days? A. Day 13 B. Day 14 C. Day 15 D. Day 16

C. decreased sensitivity. Right or left shifts in dose-response curves indicate changes in sensitivity. Changes in maximal biological response indicate changes in responsiveness. Because there is no change in maximal response, the correct answer must relate to a change in sensitivity only. A right shift indicates decreased sensitivity.

A shift to the right in the biological activity dose-response curve for a hormone with no accompanying change in the maximal response indicates: A. decreased responsiveness and decreased sensitivity. B. increased responsiveness. C. decreased sensitivity. D. increased sensitivity and decreased responsiveness. E. increased sensitivity.

D. Thyroid-stimulating hormone (TSH)

Blood levels of which of the following substances is decreased in Graves disease? A. Triiodothyronine (T3) B. Thyroxine (T4) C. Diiodotyrosine (DIT) D. Thyroid-stimulating hormone (TSH) E. Iodide (I−)

E. Aldosterone ACTH is released by the anterior pituitary and targets the adrenal cortex. Its principal actions are to regulate corticosteroid production and release (see 34·II·A). The primary regulators of aldosterone release are angiotensin II and low plasma levels of K+, whereas ACTH has only minimal effects.

Blood tests on a 34-year-old man identified high levels of circulating adrenocorticotropic hormone (ACTH). Levels of which of the following adrenal cortex hormones would be least likely to be affected by high ACTH? A. Androstenedione B. Dehydroepiandrosterone sulfate C. Cortisol D. Corticosterone E. Aldosterone

B. Osteoclasts

Calcitonin inhibits the activity of: A. Osteoblats B. Osteoclasts C. Parafollicular cells D. Thyroid

A. defects in adrenal steroidogenic enzymes. Congenital adrenal hyperplasia is the result of genetic defects that affect adrenal steroidogenic enzymes resulting in impaired formation of cortisol. Low serum cortisol is a stimulus for ACTH release from the hypothalamus. The increase in ACTH has a proliferative effect on the adrenal gland resulting in hyperplasia.

Congenital adrenal hyperplasia is most likely a result of: A. defects in adrenal steroidogenic enzymes. B. Addison disease. C. defects in ACTH secretion. D. defects in corticosteroid-binding globulin. E. Cushing disease. F. defects in aldosterone synthase.

A. Chrondrocytes Chondrocytes are the primary target for GH in the epiphyseal plate.

GH acts on which of the following cells to cause long bone growth? A. Chrondrocytes B. Osteocytes C. Intracellular matrix D. Lymphocytes

D. Increased basal body temperature with elevated progesterone level The elevated progesterone level during the luteal phase causes an increase in the patient's basal body temperature by increasing the body's thermoregulatory set point in the hypothalamus. A basal body temperature chart can be helpful to infertility patients by documenting the presence or absence of ovulation during a menstrual cycle.

How does a basal body temperature chart reflect ovulation? A. Increased basal body temperature with LH surge B. Decreased basal body temperature with LH surge C. Increased basal body temperature with decreased progesterone level D. Increased basal body temperature with elevated progesterone level E. Increased basal body temperature with increased peripheral estradiol levels

C. Decreases Progesterone causes a decrease in pulsatile release of GnRH

How does progesterone affect the pulsatile release of GnRH from the hypothalamus? A. No change B. Increases C. Decreases D. Stops release altogether

A. Mental ability would remain impaired, body growth rate would be improved, and thyroid gland size would be smaller than normal. Giving thyroid hormones to the child would improve body growth but not mental ability, because thyroid hormones are most important for CNS development in utero. Therefore, giving thyroid hormones after birth would be too late. Thyroid gland size would remain smaller than normal because thyroid hormones have no trophic effect on the gland; only TSH does.

If the 6-year-old child described in the previous question is now treated with thyroid hormones, how would mental ability, body growth rate, and thyroid gland size be affected? A. Mental ability would remain impaired, body growth rate would be improved, and thyroid gland size would be smaller than normal. B. Mental ability would be improved, body growth rate would be improved, and thyroid gland size would be normal. C. Mental ability would remain impaired, body growth rate would be improved, and thyroid gland size would be normal. D. Mental ability would remain impaired, body growth rate would be improved, and thyroid gland size would be larger than normal. E. Mental ability would be improved, body growth rate would remain slowed, and thyroid gland size would be normal. F. Mental ability would be improved, body growth rate would remain slowed, and thyroid gland size would be larger than normal.

C. GnRH receptor agonist Secretion of LH and FSH, which in turn stimulate testicular development and testosterone secretion, requires the pulsatile secretion of GnRH by the hypothalamus acting on the pituitary. Continuous stimulation of the pituitary by a GnRH agonist downregulates LH and FSH secretion. A testosterone receptor agonist would hasten puberty. FSH has minimal effects on testosterone secretion, which is required for many of the signs of puberty. Interfering with the actions of estrogens and growth hormone would not alter the events associated with puberty that are caused by testosterone.

In a young boy diagnosed with precocious puberty, puberty is best delayed by the administration of a long-lasting preparation of which of the following? A. Estrogen receptor antagonist B. FSH receptor antagonist C. GnRH receptor agonist D. Growth hormone receptor antagonist E. Testosterone receptor agonist

B. Depressed serum inhibin levels FSH stimulates the development and function of Sertoli cells. These cells secrete inhibin and growth factors that influence sperm maturation, and so serum inhibin levels would be decreased, as would growth factor secretion, by Sertoli cells. Inhibin acts mainly at the level of the pituitary to inhibit FSH secretion, and so GnRH secretion and LH secretion are affected minimally. Leydig cells would respond to LH by secreting normal levels of testostero

In experiments designed to accomplish male contraception, immunization to produce antibodies capable of both binding and neutralizing the bioactivity of human FSH is being investigated. Men immunized in this manner would be expected to exhibit which of the following? A. Depressed hypothalamic GnRH secretion B. Depressed serum inhibin levels C. Depressed serum testosterone levels D. Elevated serum LH E. Enhanced secretion of growth factors by Sertoli cells

A. with chronic adrenocortical insufficiency (Addison disease)

Increased adrenocorticotropic hormone (ACTH) secretion would be expected in patients A. with chronic adrenocortical insufficiency (Addison disease) B. with primary adrenocortical hyperplasia C. who are receiving glucocorticoid for immunosuppression after a renal transplant D. with elevated levels of angiotensin II

C. Stimulate bone resorption, leading to the release of calcium into the plasma One of the major actions of PTH is on bone. Binding of PTH to receptors on bone cells stimulates bone resorption, particularly in the presence of permissive amounts of vitamin D. This leads to the release of calcium phosphate and the elevation of plasma levels of both calcium and phosphate. Separately, PTH can act on the gastrointestinal tract to stimulate calcium absorption and on the renal thick ascending limb and distal convoluted tubule to stimulate calcium reabsorption. Hence, PTH plays a major role in regulating plasma calcium levels through its actions on calcium handling by several organ systems.

Parathyroid hormone plays a critical role in regulating plasma calcium levels, as is evident in individuals with hyperparathyroidism, in which persistent hypercalcemia is evident. Under normal conditions, low plasma calcium stimulates PTH secretion, which in turn activates and/or inhibits calcium-handling processes at a number of different sites. High PTH levels stimulate and/or inhibit which of the following processes to return plasma calcium levels toward normal? A. Inhibit calcium secretion by the gastrointestinal tract B. Reduce the expression of plasma calcium-binding proteins C. Stimulate bone resorption, leading to the release of calcium into the plasma D. Stimulate calcium reabsorption by the renal proximal tubule E. Stimulate the release of calcium from muscle cells

You can do all things through Christ who strengthens you!

Philippians 4:13

B. dilation of the cervix

Secretion of oxytocin is increased by A. milk ejection B. dilation of the cervix C. increased prolactin levels D. increased extracellular fluid (ECF) volume E. increased serum osmolarity

A. Aldosterone

Selective destruction of the zona glomerulosa of the adrenal cortex would produce a deficiency of which hormone? A. Aldosterone B. Androstenedione C. Cortisol D. Dehydroepiandrosterone E. Testosterone

E. Inhibiting cGMP phosphodiesterase

Slidenafil citrate enhances oenile erections by: A. Activating cAMP phosphodiesterase B. Activating cGMP phosphodiesterase C. Activating guananyl cyclase D. Inhibiting cAMP phosphodiesterase E. Inhibiting cGMP phosphodiesterase F. Inhibiting guananyl cyclase

D. signal amplification. Hormones generally circulate at concentrations from 10−9 to 10−12 M. They produce much larger changes in a variety of biological parameters as a result of signal amplification, in which the rather weak hormonal signal is amplified into a larger biological response.

The ability of hormones to be effective regulators of biological function despite circulating at very low concentrations results from: A. the multiplicity of their effects. B. transport proteins. C. pleiotropic effects. D. signal amplification. E. competitive binding.

B. Somatomedins Somatomedins, also known as IGFs, are produced in response to GH by the liver and locally by GH target cells. Those produced by the liver enter the circulation and act in an endocrine fashion, whereas those produced locally act in a paracrine or autocrine fashion by binding to specific IGF receptors. Many GH actions are mediated by IGFs.

The actions of GH are mediated in part by which of the following? A.Insulin B. Somatomedins C. Thyroid hormone D. Estrogen

E. positive feedback of estrogen on the anterior pituitary

The cause of the sudden increase shown at point E is A. negative feedback of progesterone on the hypothalamus B. negative feedback of estrogen on the anterior pituitary C. negative feedback of follicle-stimulating hormone (FSH) on the ovary D. positive feedback of FSH on the ovary E. positive feedback of estrogen on the anterior pituitary

A. stimulation of endocytosis of thyroglobulin stored in the colloid. TSH stimulates the endocytosis of colloid by the apical membrane of the follicular cell. Thyroglobulin in the colloid is then hydrolyzed in the lysosomal vesicles to release thyroid hormones. T3 and T4 are stored in thyroglobulin in the colloid, not in secretory vesicles in the follicle cell. TSH stimulates the uptake of iodide from the blood, not the colloid. It has no effect on blood flow to the thyroid gland and no direct effect on the binding of T3 and T4 to thyroxine-binding globulin. TSH stimulates an increase in cAMP not an increase in the hydrolysis of this second messenger.

The effects of TSH on thyroid follicular cells include: A. stimulation of endocytosis of thyroglobulin stored in the colloid. B. release of a large pool of T4 and T3 stored in secretory vesicles in the cell. C. stimulation of the uptake of iodide from the thyroglobulin stored in the colloid. D. Increase in perfusion by the blood. E. stimulation of the binding of T4 and T3 to thyroxine-binding globulin. F. increased cAMP hydrolysis.

B. Dihydrotestosterone

The hormone that is essential for intrauterine development of male external genitalia is: A. Testosterone B. Dihydrotestosterone C. Mullerian regression factor D. SOX factor

G. fetal adrenal gland, fetal liver, and placenta During the second and third trimesters of pregnancy, the fetal adrenal gland synthesizes dehydroepiandrosterone sulfate (DHEA-S), which is hydroxylated in the fetal liver and then transferred to the placenta, where it is aromatized to estrogen. In the first trimester, the corpus luteum is the source of both estrogen and progesterone.

The source of estrogen during the second and third trimesters of pregnancy is the A. corpus luteum B. maternal ovaries C. fetal ovaries D. placenta E. maternal ovaries and fetal adrenal gland F. maternal adrenal gland and fetal liver G. fetal adrenal gland, fetal liver, and placenta

C. corpus luteum

The source of the increase in concentration at point D is the A. ovary B. adrenal cortex C. corpus luteum D. hypothalamus E. anterior pituitary

D. Y chromosome

The testis-determining gene (or the SRY gene) is located normally on/in: A. Chromosone 6 B. Chromosone 12 C. Short arm of chromosone 22 D. Y chromosome

E. Unbound Blood-binding proteins, such as albumin and thyroxine-binding globulin, are important in maintaining a circulating "pool" of T3 and T4 (see 35·II). However, although bound, hormones such as T3 and T4 are not biologically active.

Triiodothyronine (T3) and thyroxine (T4) have a multitude of peripheral effects. In what form are T3 and T4 most biologically active? A. Bound to albumin B. Bound to transthyretin C. Bound to thyroglobulin D. Bound to thyroxine-binding globulin E. Unbound

F. can be produced by the deiodination of T4 in pituitary thyrotrophs. T3 is produced from T4 by 5′-deiodinase D2 in the anterior pituitary. The major thyroid hormone product of the thyroid gland is T4. The thyroid hormone receptor (TR) is located in the nucleus. The 5-deiodinase D3 acts on T4, to make reverse T3. The half-life of T3 in the bloodstream is about 1 day because of the protective actions of the thyroid hormone-binding proteins. Thyroid peroxidase catalyzes the iodination of thyroglobulin to form MIT and DIT, the precursor molecules for T3. Release of T3 from thyroglobulin is catalyzed by proteases in the lysosomal vesicles.

Triiodothyronine (T3): A. is produced in greater amounts by the thyroid gland than T4. B. is bound by the thyroid receptor present in the cytosol of target cells. C. is formed from T4 through the action of the 5-deiodinase D3. D. has a half-life of a few minutes in the bloodstream. E. is released from thyroglobulin through the action of thyroid peroxidase. F. can be produced by the deiodination of T4 in pituitary thyrotrophs.

C. dissipate the proton gradient across the mitochondrial membrane to generate heat. Uncoupling proteins allow protons to flow down their concentration gradient across the mitochondrial membrane, uncoupled from the synthesis of ATP. The resulting energy generated is released as heat, and ATP is not synthesized. Uncoupling proteins are increased by thyroid hormones. The novel uncoupling proteins are found in many tissues, including muscle and adipose tissue. Fatty acid and glucose oxidation are not coupled in mitochondria, and the uncoupling proteins are not the switch between oxidation of these two substrates. Uncoupling proteins have not been demonstrated to be absolutely essential to the maintenance of body temperature in mammals. However, UCP-1 is important in the ability of small mammals, such as rodents, to tolerate cold temperatures.

Uncoupling proteins: A. use the proton gradient across the mitochondrial membrane to facilitate ATP synthesis. B. are decreased by thyroid hormones C. dissipate the proton gradient across the mitochondrial membrane to generate heat. D. are present exclusively in brown fat. E. uncouple fatty acid oxidation from glucose oxidation in mitochondria. F. are essential for maintaining body temperature in mammals.

C. Progesterone

Use the graph which shows changes during the menstrual cycle Blood levels of which substance are described by curve B? A. Estradiol B. Estriol C. Progesterone D. Follicle-stimulating hormone (FSH) E. Luteinizing hormone (LH)

B. progesterone on the hypothalamus

Use the graph which shows changes during the menstrual cycle The increase shown at point A is caused by the effect of A. estrogen on the anterior pituitary B. progesterone on the hypothalamus C. follicle-stimulating hormone (FSH) on the ovary D. luteinizing hormone (LH) on the anterior pituitary E. prolactin on the ovary

D. ovary

Use the graph which shows changes during the menstrual cycle The source of the increase in concentration indicated at point C is the A. hypothalamus B. anterior pituitary C. corpus luteum D. ovary E. adrenal cortex

E. Catecholamines stimulate gluconeogenesis in the liver. Catecholamines stimulate glycogenolysis and gluconeogenesis in the liver, causing glucose to be synthesized and released into the blood. Catecholamines stimulate glycogen phosphorylase in muscle to free glucose for use by the muscle

What is the mechanism through which catecholamines stabilize blood glucose concentration in response to hypoglycemia? A. Catecholamines stimulate glycogen phosphorylase to release glucose from muscle. B. Catecholamines inhibit glycogenolysis in the liver. C. Catecholamines stimulate the release of insulin from the pancreas. D. Catecholamines inhibit the release of fatty acids from adipose tissue. E. Catecholamines stimulate gluconeogenesis in the liver. F. Catecholamines inhibit the release of lactate from muscle.

C. Parathyroid hormone Vitamin D derivatives (1,25-dihydroxyvitamin D3 and, to a lesser extent, 7-dehydrocholesterol) function by increasing renal reabsorption of both Ca2+and PO43− (see 35·IV·3). Parathyroid hormone increases reabsorption of Ca2+ but decreases PO43− reabsorption.

Which of the following Ca2+ regulatory hormones has a mechanism of action best described as increasing Ca2+ resorption from bone and reabsorption in the renal distal convoluted tubule, while also decreasing PO43− reabsorption in the renal proximal tubule? A. 1,25-Dihydroxyvitamin D3 B. 7-Dehydrocholesterol C. Parathyroid hormone D. Calcitonin E. Calsequestrin

A. Decreased blood volume Decreased blood volume stimulates the secretion of renin (because of decreased renal perfusion pressure) and initiates the renin-angiotensin-aldosterone cascade.

Which of the following causes increased aldosterone secretion? A. Decreased blood volume B. Administration of an inhibitor of angiotensin-converting enzyme (ACE) C. Hyperosmolarity D. Hypokalemia

C. Loss of hypothalamic neurons Destruction of the neurons in the paraventricular nuclei of the hypothalamus decreases CRH release, which, in turn, causes decreased synthesis and secretion of ACTH.

Which of the following conditions is consistent with a decreased rate of ACTH secretion? A. Hyperosmolality of the blood B. Low serum glucocorticoid C. Loss of hypothalamic neurons D. Primary adrenal insufficiency E. Stress as a result of emotional trauma F. Increased PKA activity in corticotrophs

E. Chronic renal failure

Which of the following decreases the conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol? A. A diet low in Ca2+ B. Hypocalcemia C. Hyperparathyroidism D. Hypophosphatemia E. Chronic renal failure

D. Blood levels of estrogen and progesterone are high

Which of the following explains the suppression of lactation during pregnancy? A. Blood prolactin levels are too low for milk production to occur B. Human placental lactogen levels are too low for milk production to occur C. The fetal adrenal gland does not produce sufficient estriol D. Blood levels of estrogen and progesterone are high E. The maternal anterior pituitary is suppressed

A. Synthesis of inhibin

Which of the following functions of the Sertoli cells mediates negative feedback control of follicle-stimulating hormone (FSH) secretion? A. Synthesis of inhibin B. Synthesis of testosterone C. Aromatization of testosterone D. Maintenance of the blood-testes barrier

A. Inhibin B Inhibin from the ovary inhibits the release of FSH from the pituitary

Which of the following hormone peaks during the mid-luteal phase? A. Inhibin B B. FSH C. LH D. GnRH

E. Gonadotropin-releasing hormone (GnRH)

Which of the following hormones acts by an inositol 1,4,5-triphosphate (IP3)-Ca2+ mechanism of action? A. 1,25-Dihydroxycholecalciferol B. Progesterone C. Insulin D. Parathyroid hormone (PTH) E. Gonadotropin-releasing hormone (GnRH)

A. Thyroid hormone Thyroid hormone, an amine, acts on its target tissues by a steroid hormone mechanism, inducing the synthesis of new proteins.

Which of the following hormones acts on its target tissues by a steroid hormone mechanism of action? A. Thyroid hormone B. Parathyroid hormone (PTH) C. Antidiuretic hormone (ADH) on the collecting duct D. β1-adrenergic agonists E. Glucagon

E. Aldosterone Aldosterone binds to mineralocorticoid receptors in target cells, and the complex is then translocated to the nucleus, where it binds to a mineralocorticoid response element on DNA. Insulin, growth hormone, and insulin-like growth factor bind to receptors that contain or are associated with a tyrosine kinase. Epinephrine also binds to cell membrane receptors, of either the α- or β-adrenergic variety. All of the cell membrane receptors mentioned can have genomic effects by stimulating various pathways but not via direct binding to DNA.

Which of the following hormones most likely binds to a cytosolic receptor that then translocates to the nucleus to induce transcriptional changes? B. Growth hormone C. Insulin-like growth factor D. Epinephrine E. Aldosterone

E. Thyroid-stimulating hormone (TSH)

Which of the following hormones originates in the anterior pituitary? A. Dopamine B. Growth hormone-releasing hormone (GHRH) C. Somatostatin D. Gonadotropin-releasing hormone (GnRH) E. Thyroid-stimulating hormone (TSH) F. Oxytocin G. Testosterone

D. Somatomedins

Which of the following inhibits the secretion of growth hormone by the anterior pituitary? A. Sleep B. Stress C. Puberty D. Somatomedins E. Starvation F. Hypoglycemia

A. Insulin The insulin receptor in target tissues is a tetramer. The two β subunits have tyrosine kinase activity and autophosphorylate the receptor when stimulated by insulin.

Which of the following pancreatic secretions has a receptor with four subunits, two of which have tyrosine kinase activity? A. Insulin B. Glucagon C. Somatostatin D. Pancreatic lipase

B. Stimulation of Ca2+ reabsorption in the distal tubule

Which of the following results from the action of parathyroid hormone (PTH) on the renal tubule? A. Inhibition of 1α-hydroxylase B. Stimulation of Ca2+ reabsorption in the distal tubule C. Stimulation of phosphate reabsorption in the proximal tubule D. Interaction with receptors on the luminal membrane of the proximal tubular cells E. Decreased urinary excretion of cyclic adenosine monophosphate (cAMP)

B. Cholesterol in LDL particles Cholesterol esters in LDL sources are the most important source of cholesterol for sustaining adrenal steroidogenesis when it occurs at a high rate over a long period of time. This cholesterol can be used directly after release from LDL and not stored. De novo synthesis of cholesterol from acetate is a minor source of cholesterol in humans. Cholesterol from the plasma membrane or endoplasmic reticulum is not used for steroidogenesis. Cholesterol esters in lipid droplets within adrenal cortical cells would be used first and depleted during periods of high adrenal steroid hormone synthesis.

Which of the following sources of cholesterol is most important for sustaining adrenal steroidogenesis when it occurs at a high rate for a long time? A. De novo synthesis of cholesterol from acetate B. Cholesterol in LDL particles C. Cholesterol in the plasma membrane D. Cholesterol in lipid droplets within adrenal cortical cells E. Cholesterol from the endoplasmic reticulum F. Cholesterol in lipid droplets within adrenal medullary cells

D. They stimulate the expression of the GH gene in somatotrophs. Thyroid hormones stimulate the expression of the GH gene in somatotrophs. Thyroid hormones exert a negative feedback signal on the hypothalamic-pituitary-thyroid axis to inhibit their own synthesis and secretion. Therefore, thyroid hormones decrease the sensitivity of thyrotrophs to TRH, decrease the formation of IP3 in thyrotrophs, inhibit the expression of the genes for the α and β subunits of TSH in thyrotrophs, and decrease the secretion of TSH by thyrotrophs. Thyroid hormones have no effect on ACTH release.

Which of the following statements most accurately describes the feedback effects of thyroid hormones? A. They increase the sensitivity of thyrotrophs to TRH. B. They stimulate transcription of the α and β subunits of TSH in thyrotrophs. C. They increase the secretion of TSH by thyrotrophs. D. They stimulate the expression of the GH gene in somatotrophs. E. They increase IP3 in thyrotrophs. F. They increase ACTH release.

A. Adrenocorticotropic hormone (ACTH)

Which of the following substances is derived from proopiomelanocortin (POMC)? A. Adrenocorticotropic hormone (ACTH) B. Follicle-stimulating hormone (FSH) C. Melatonin D. Cortisol E. Dehydroepiandrosterone

H. Increased triiodothyronine (T3) levels

Which of the following would be expected in a patient with Graves disease? A. Cold sensitivity B. Weight gain C. Decreased O2 consumption D. Decreased cardiac output E. Drooping eyelids F. Atrophy of the thyroid gland G. Increased thyroid-stimulating hormone (TSH) levels H. Increased triiodothyronine (T3) levels

A. Cholesterol → pregnenolone The conversion of cholesterol to pregnenolone is catalyzed by cholesterol desmolase. This step in the biosynthetic pathway for steroid hormones is stimulated by adrenocorticotropic hormone (ACTH).

Which step in steroid hormone biosynthesis is stimulated by adrenocorticotropic hormone (ACTH)? A. Cholesterol → pregnenolone B. Progesterone → 11-deoxycorticosterone C. 17-Hydroxypregnenolone → dehydroepiandrosterone D. Testosterone → estradiol E. Testosterone → dihydrotestosterone

E. Testosterone → dihydrotestosterone Some target tissues for androgens contain 5α-reductase, which converts testosterone to dihydrotestosterone, the active form in those tissues.

Which step in steroid hormone biosynthesis occurs in the accessory sex target tissues of the male and is catalyzed by 5α-reductase? A. Cholesterol → pregnenolone B. Progesterone → 11-deoxycorticosterone C. 17-Hydroxypregnenolone → dehydroepiandrosterone D. Testosterone → estradiol E. Testosterone → dihydrotestosterone

C. 17-Hydroxypregnenolone → dehydroepiandrosterone The conversion of 17-hydroxypregnenolone to dehydroepiandrosterone (as well as the conversion of 17-hydroxyprogesterone to androstenedione) is catalyzed by 17,20-lyase. If this process is inhibited, synthesis of androgens is stopped.

Which step in steroid hormone biosynthesis, if inhibited, blocks the production of all androgenic compounds but does not block the production of glucocorticoids? A. Cholesterol → pregnenolone B. Progesterone → 11-deoxycorticosterone C. 17-Hydroxypregnenolone → dehydroepiandrosterone D. Testosterone → estradiol E. Testosterone → dihydrotestosterone

D. Only testes develop

With regard to development of gonads, which of the following is most likely with a 46 XX zygote that contains a functional SRY gene? A. Female internal and external genitalia develop B. Both ovaries and testes develop C. Only ovaries develop D. Only testes develop

C. Progesterone Withdrawal of the hormone progesterone results in sloughing of the endometrium (menstruation). If pregnancy occurs, the corpus luteum is "rescued" and production of progesterone continues (no menstruation).

Withdrawal of which of the following hormones results in menstruation? A. Estradiol B. FSH C. Progesterone D. LH

C. the presence of specific receptors on target cells. Hormones produce their effects on target cells by interacting with specific receptors. Hormone binding to its receptor generally initiates a cascade of events that lead to biological effects in the target cells.

Within the endocrine system, specificity of communication is determined by: A. the chemical nature of the hormone. B. the distance between the endocrine cell and its target cell(s). C. the presence of specific receptors on target cells. D. anatomic connections between the endocrine and target cells. E. the affinity of binding between the hormone and its receptor.