Endocrinology, Vitamins and Nutrition
The most common method for testing for Vitamin C (ascorbic acid) is:
2,4-dinitrophenylhydrazine
Which adipokine is decreased in obesity, is anti-inflammatory, and increases insulin sensitivity? Leptin Resistin TNF-a Adiponectin
Adiponectin Adiponectin is a protective cytokine synthesized and secreted almost exclusively by the adipocytes. This cytokine is anti-inflammatory and increases insulin sensitivity. Levels of adiponectin are decreased in weight gain, obesity, and in those who are insulin resistant. Leptin is synthesized and released from adipose cells in response to adipose tissue changes. It reduces intracellular lipid levels in many types of body cells and thus improves insulin sensitivity, but is usually increased in obesity NOT decreased. It is an appetite suppressant and inhibitor of fatty liver formation. Resistin is another inflammatory cytokine that is increased in obesity. It increases insulin resistance and enhances adhesion molecules present on endothelial cells. It is synthesized and secreted by macrophages and adipocytes. Adipocyte-secreted TNF-a stimulates adipocytes to increase their release of non-esterified fatty acids and decrease adiponectin synthesis. TNF-a also inhibits insulin activity, leading to insulin resistance. Adipocyte TNF-a secretion is increased in obesity causing increased insulin resistance in obesity.
Hormonal variation throughout the menstrual cycle typically shows: An abrupt rise in luteinizing hormone (LH) 3-36 hours prior to ovulation Progesterone peaking at ovulation then falling Estrogen peaking at ovulation then falling An abrupt decrease of LH 3-36 hours prior to ovulation
An abrupt rise in luteinizing hormone (LH) 3-36 hours prior to ovulation The LH surge is required for ovulation. In fact, 3-36 hours after the LH surge, the follicle releases an ovum, which is called ovulation. After ovulation, the corpus luteum produces large amounts of progesterone while estrogen levels are also increased in order to prepare the uterus for a possible pregnancy.
The production of neutral 17-ketosteroids is a measure of which of the following? Cholesterol production Androgen production Estrogen production Growth hormone
Androgen production 17-ketosteroids are metabolites of male steroid sex hormones or androgens, and other hormones released by a part of the adrenal gland in males and females, and in the testes in males. The majority of testosterone is produced in the testes and the adrenal cortex. About 1/3 of total urine 17-KSs in men are metabolites of testosterone with the rest derived from steroids produced by the adrenal glands. In women, just about all of the 17-KSs are derived directly from the steroids produced by the adrenal glands.
Deficiency in Vitamin B1 (thiamine) is associated with:
Beriberi (nerve inflammation + heart failure)
Which enzyme is responsible for the rate-limiting step of steroid hormone synthesis? 21-hydroxylase CYP450 F-zone enzymes 17-hydroxylase
CYP450 17- and 21-hydroxylases are enzymes that hydroxylate their specific carbons in steroidogenesis but not the rate-limiting step, while F-zone enzymes convert pregnenolone into further steroid products.
Which of the following action describes the MAJOR property of antidiuretic hormone? The correct answer is highlighted below Acts on proximal tubules. Changes distal tubule water permeability Acts on Na/K/(H') pump Cannot be affected by diuretics
Changes distal tubule water permeability Antidiuretic hormone, or ADH, has the important role of conserving body water by reducing the loss of water in urine by changing the water permeability of the distal tubule and collecting duct. An increase in ADH causes concentrated urine since the water is retained and absorbed through the permeable membrane. A decrease in ADH causes the collecting ducts to retain very little water, instead, it is excreted as urine.
An elevated level of which of the following hormones will inhibit pituitary secretion of adrenocorticotropic hormone (ACTH)? Aldosterone Cortisol Testosterone Progesterone
Cortisol is part of the negative feedback mechanism for ACTH. So, elevated levels of cortisol stimulate the pituitary gland to inhibit the secretion of ACTH. The hypothalamic-pituitary-end organ negative feedback system that controls cortisol release follows the steps: Hypothalamus releases corticotropin-releasing hormone (CRH) which is delivered to the anterior pituitary. CRH triggers the release of ACTH by the anterior pituitary. Antidiuretic hormone (ADH) and pro-inflammatory cytokines can also independently trigger ACTH release. ACTH triggers the synthesis and release of cortisol from the adrenal glands. Increased cortisol levels feedback at the anterior pituitary (to stop ACTH release) and hypothalamus (to stop CRH) respectively. Hypothalamus is the major site of this negative feedback from cortisol.
A patient with truncal obesity, hypertension, a ruddy/striated complexion, and mood swings has multiple elevated glucose values. A fasting ACTH sample is also elevated. The physician orders a dexamethasone test, which shows an elevated cortisol level (no suppression). What is the most likely cause for the patient's values and symptoms? Addison's Disease Cushing Syndrome Cushing Disease Diabetes
Cushing Syndrome ACTH is released from the anterior pituitary and controls the production of cortisol from the adrenal glands, specifically in the zona fasciculata. Cortisol promotes gluconeogenesis and glycogenolysis increasing glucose. The dexamethasone suppression test is used to help diagnose the cause of increased cortisol. Dexamethasone testing showed elevated cortisol (no suppression), indicating the problem is therefore with an overproduction of ACTH from an ectopic ACTH-producing tumor. Cushing's disease is a pituitary tumor that produces ACTH, however, the dexamethasone test will shut off the ACTH production in this case, therefore dropping the cortisol production and showing a lower level. Addison's disease is a decreased cortisol level and therefore low blood pressure, glucose level, and dizziness/fatigue. Diabetes may account for elevated glucose, but not the levels of ACTH and cortisol.
A 64-year old man lost 15 pounds, became weaker, and his face became fuller with a ruddy complexion. His laboratory tests revealed: Serum cortisol 8 AM: 880 nmol/L, 138-635 nmol/L (reference range) 4 PM: 828 nmol/L, 83-414 nmol/L (reference range) After these results, an overnight dexamethasone suppression test gave a cortisol level of 773 nmol/L. The MOST probable diagnosis for this patient is: Congenital adrenal hyperplasia Addison's disease Cushing's Syndrome Conn's Syndrome
Cushing's Syndrome Cushing's syndrome is a hormonal disorder caused by the effects of an individual having high levels of cortisol. One of the signs of this condition is skin, which becomes fragile and thin and a rounding, or fullness of the face. More than one test is performed to diagnose Cushing's syndrome and includes the 24-hour urinary free cortisol test, measurement of day and night cortisol levels, and the low-dose dexamethasone suppression test. Cortisol production is normally suppressed at night, but in Cushing's syndrome, this suppression doesn't occur. If the cortisol level is more than 50 nmol/L, Cushing's syndrome is suspected. In the dexamethasone suppression test, cortisol signals the pituitary to release less ACTH, so the normal response after taking dexamethasone is a decrease in blood and urine cortisol levels; if cortisol levels do not decrease (such as in this case), Cushing's syndrome is suspected.
In patients with suspected primary hypothyroidism associated with Hashimoto's thyroiditis, one would expect the following laboratory test results: T4 ___? TSH ___? TRH stimulation ___? Increased, decreased, increased Decreased, increased, increased Increased, decreased, decreased Increased, increased, decreased
Decreased, increased, increased In Hashimoto's thyroiditis antibodies react against proteins in the thyroid gland, causing gradual destruction of the gland itself and making the gland unable to produce the thyroid hormones the body needs. Therefore the T4 is decreased, but the TSH is increased since the pituitary gland is attempting to stimulate the failing thyroid gland. The TRH stimulation is increased since the pituitary gland is working and is able to produce elevated levels of TSH upon TRH stimulation.
Which of the following would you find in a primary hyperparathyroidism case? The correct answer is highlighted below Elevated serum calcium and decreased serum phosphorus Elevated serum calcium and elevated serum phosphorus Decreased serum calcium and decreased serum phosphorus Decreased serum calcium and increased serum phosphorus
Elevated serum calcium and decreased serum phosphorus Primary hyperparathyroidism is a disorder of the parathyroid glands where overactive parathyroid glands secrete too much parathyroid hormone (PTH). This excess PTH triggers the release of too much calcium into the bloodstream.
The most common testing method for vitamin E determination is by:
High-performance liquid chromatography (HPLC)
Calcium and phosphorus levels were determined for a 4-year-old patient as follows: Ca - 14 mg/dL Phosphorus - 1 mg/dL These results are MOST compatible with: Hyperparathyroidism Renal failure Rickets Hypervitaminosis
Hyperparathyroidism Decreased levels of phosphorus are often associated with increased renal excretion as with hyperparathyroidism. If the patient was in renal failure, the phosphorus levels would most likely not be decreased. Rickets is a condition seen in young children due to vitamin D deficiency. Calcium levels are usually low or normal, which is not the case for this example. Hypervitaminosis can lead to elevations in calcium, but since this is a child that scenario is not likely.
The substance produced by the pancreas and released in the bloodstream to help glucose absorption by the tissues is called? Iodine Insulin Diabetes Ethanol
Insulin
Which of the following hormones is mainly responsible for the entry of glucose into the cell for energy production? Epinephrine Glucagon Cortisol Insulin
Insulin is the hormone that is mainly responsible for the entry of glucose into the cell for energy production. Insulin is produced by the ß-cells of islets of Langerhans in the pancreas. Glucagon and epinephrine promote glycogenolysis, conversion of glycogen to glucose, which increases plasma glucose. Cortisol, along with glucagon, increases gluconeogenesis, formation of glucose from noncarbohydrates, which also raises plasma glucose concentration.
Pernicious anemia refers to cobalamin deficiency that results from a lack of which of the following? Vitamin B12 Intrinsic Factor Folate Vitamin C
Intrinsic Factor More commonly referred to as Vitamin B12, Cobalamin requires Intrinsic Factor to be absorbed and available for use. In most instances of pernicious anemia, there is not a true deficiency of vitamin B12. It's just not being absorbed due to a lack of IF. Folate (Folic Acid) deficiency can cause a hematologic disorder that appears similar to vitamin B12 deficiency but is not required for B12 absorption. Vitamin C is not required for Vitamin B12 absorption.
Which one of the following statements about thyroid-stimulating hormone (TSH) is true? It is decreased in hyperthyroidism. It is decreased in hypothyroidism. A sensitive TSH assay is not a good screening test for thyroid function. Diffuse toxic goiter is associated with elevated TSH levels.
It is decreased in hyperthyroidism. In the absence of pituitary and hypothalamic disease, TSH is decreased in hyperthyroidism and increased in hypothyroidism, with few exceptions. A sensitive TSH assay is now considered the most cost-effective method of screening for thyroid disorders. Diffuse toxic goiter is a cause of primary hyperthyroidism and would be associated with decreased TSH.
From the groups of analytes below, which set would most likely be INCREASED in type 1 diabetic patients in crisis? Insulin and blood glucose Insulin and ketone bodies Ketone bodies and blood glucose Ketone bodies and blood pH
Ketone bodies and blood glucose A type 1 diabetic with elevated blood glucose and lack of insulin production in a crisis can become ketotic and go into a ketoacidosis coma. Excess ketone bodies are produced along with increased blood glucose. The acidosis results in a decreased pH.
Which one of the following adipocyte products is an important messenger in metabolism, signaling the hypothalamus that there are changes in fat stores? Leptin Resistin IL-6 Angiotensinogen
Leptim Leptin signals the hypothalamus that there are changes in fat stores. Leptin is synthesized and released from adipose cells in response to adipose tissue changes. It reduces intracellular lipid levels in many types of body cells and thus improves insulin sensitivity. It is an appetite suppressant and inhibitor of fatty liver formation. Resistin increases insulin resistance and enhances adhesion molecules present on endothelial cells. Resistin is another inflammatory cytokine that is increased in obesity. It is synthesized and secreted by macrophages and adipocytes. IL-6 responds to tissue injury. IL-6 increases insulin resistance by inhibiting insulin receptor signal transduction in liver cells. It also increases other inflammatory cytokines, interleukin-1 (IL-1) and TNF-a, and stimulates the liver to produce C-reactive protein (CRP). Adipose tissue and liver cells produce angiotensinogen, a precursor of angiotensin II. Besides increasing blood pressure, angiotensin II may stimulate adipose cell formation and thus increase adipose mass.
Albumin levels are can be a good gauge for chronic protein deficiency. Which of the following terms describes inadequate protein and caloric intake? Kwashiorkor Marasmus Albuminemia Hypoproteinism
Marasmus - nutritional disease resulting from calorie deprivation and insufficient protein. Kwashiorkor is a nutritional disease resulting from protein deprivation. Albuminemia is not a term that is commonly used. It would only point to album and not other proteins. Hypoproteinism is not a term that is used. Hypoproteinemia is a term that can be used to describe low levels of protein in the blood
Serum calcitonin is typically elevated in which of the following conditions? Medullary carcinoma of the thyroid Hyperthyroidism Glioblastoma Adrenal adenoma
Medullary carcinoma of the thyroid Serum calcitonin is normally produced by the C cells of the thyroid. It functions to reduce serum calcium by inhibiting the release of calcium from bone. It is a peptide with a molecular weight of 3,400 and has a half-life of approximately 12 minutes. It is characteristically elevated in medullary carcinoma of the thyroid. Since medullary carcinoma often occurs as an autosomal disorder, family members of patients with this condition should be screened for serum calcitonin. It is not associated with hyperthyroidism, glioblastoma, or adrenal adenoma.
Enzyme-multiplied immunoassay techniques (EMIT) differ from all other types of enzyme immunoassays in that: Lysozyme is the only enzyme used to label the hapten molecule. No separation of bound and free antigen is required. Inhibition of the enzyme label is accomplished with polyethylene glycol. Antibody absorption to polystyrene tubes precludes competition to labeled and free antigens.
No separation of bound and free antigen is required. EMIT utilizes a technique where the patient sample is incubated with antibodies directed against a drug present. After the incubation period, an enzyme-labeled drug is added and binds to any available binding sites left on the antibody in the sample mixture. There is no separation step required in the EMIT procedure as the unbound labeled drug antigen portion only is measured through the reaction. This amount of free enzyme-labeled drug is compared to a standard curve to obtain patient results.
In healthy individuals, calcitonin is synthesized by which cells in the body? Hepatocytes Leukocytes Thyroid C cells Red blood cells
ONLY synthesized by Thyroid C cells. Inhibits bones from further releasing calcium
What would the following Schilling test results indicate: Part I: 2% excretion of radioactive vitamin B12 (normal: 5-35%) Part II: 8% excretion of radioactive vitamin B12 after intrinsic factor was given with vitamin B12 (normal: 7-10%). Tropical sprue Transcobalamin deficiency Folic acid deficiency Pernicious anemia
Pernicious anemia In part I of the Schilling test, the patient is given labeled B12 orally, followed by a flushing dose of B12 injected intramuscularly. If IF (Intrinsic Factor) is present, normal absorption occurs, and the labeled Vitamin B12 is rapidly excreted. If part I is abnormal, part II is performed. In part II, the test is repeated with the addition of IF to the oral dose to determine if malabsorption is caused b a lack of IF. If the Schilling test result is normal in Part II, a deficiency of IF is confirmed, and a diagnosis of Pernicious anemia is confirmed. Pernicious anemia is a chronic disease caused by the deficiency of IF. Tropical Sprue is an acquired disease that causes malabsorption of B12, resulting in megaloblastic anemia. The results of Part II of the Schilling test remain uncorrected because Tropical Sprue is not corrected with the addition of IF. Transcobalamin deficiency is a genetic disorder that impairs the transport of vitamin B12. The results of the Schilling test remain uncorrected and abnormal because Transcobalimin deficiency is uncorrected with the addition of IF. Folic acid deficiency results in megaloblastic anemia. The Schilling test is only utilized to evaluate megaloblastic anemias due to B12 deficiency or malabsorption.
One method to test for Vitamin B12 is:
Protein binding radioimmunoassay (RIA)
The active form of Vitamin B6 is:
Pyridoxal phosphate
All of the following are characteristics of type 2 diabetes mellitus EXCEPT: Insulin levels may or may NOT be abnormal. More common than type 1 diabetes. Requires insulin therapy to control hyperglycemia. It commonly occurs in adults.
Requires insulin therapy to control hyperglycemia. In type 1 diabetes mellitus, patients have a deficiency in producing insulin from the beta cells in the islets of Langerhans of the pancreas. In this type of diabetes, patients are often children and are given exogenous insulin therapy to control hyperglycemia. Type 2 diabetes mellitus commonly occurs in adults and involves the body's unresponsiveness to insulin, in which exogenous insulin therapy does not commonly treat the condition.
Deficiency in Vitamin D (fat-soluble) is associated with:
Rickets (young) or osteomalacia (adult)
Deficiency in Vitamin C is associated with:
Scurvy
Patients with Cushing's disease typically exhibit: Decreased plasma 17-hydroxysteroid concentration Decreased urinary 17-hydroxysteroid excretion Serum cortisol overproduction Decreased cortisol secretion rate
Serum cortisol overproduction Cushing's disease is a hormone disorder caused by a pituitary tumor secreting too much adrenocorticotropic hormone (ACTH), which causes the adrenal glands to produce too much cortisol. Serum cortisol may be greater than 15 mg/dL. The serum reference range for cortisol is approximately 0.006 - 0.023 mg/dL, which is usually expressed as 6 - 23 micrograms per deciliter (µg/dL).
Which of the following describes gastrin's role in digestion? Stimulates gastric acid-HCl secretion Stimulates secretion of a base to lower the stomach's pH Is secreted when the gastric fluid pH is low to buffer fluid Inhibits the secretion of intrinsic factor
Stimulates gastric acid-HCl secretion Gastrin is secreted by the gastrointestinal mucosa cells in response to mechanical stress or high pH, both of which are produced by the presence of food in the stomach. Gastrin stimulates the stomach parietal cells to produce gastric hydrochloric acid.
The measurement of 17-ketosteroids (17-KSs) in urine is performed to assess PRIMARILY which organ(s)? Testes Adrenal cortex Testes and adrenal cortex Anterior pituitary
Testes and adrenal cortex 17-ketosteroids are metabolites of testosterone and adrenal steroid hormones. The majority of testosterone is produced in the testes and the adrenal cortex. About 1/3 of total urine 17-KSs in men are metabolites of testosterone with the rest derived from steroids produced by the adrenal glands. In women, just about all of the 17-KSs are derived directly from the steroids produced by the adrenal glands.
A patient with renal failure is seen for blood work. What would you expect the serum calcium and phosphorus levels to be in this patient? Increased calcium and phosphorus levels Decreased calcium and phosphorus levels Increased calcium but decreased phosphorus levels Decreased calcium but increased phosphorus levels
The correct answer is decreased calcium and increased phosphorus. This is because damaged kidneys (like those seen in renal failure) cannot complete the second hydroxylation of vitamin D to the active 1,25 form. Therefore vitamin D is not active and cannot increase calcium levels in the blood, which leads to low levels. Also, the diseased kidneys cannot absorb calcium and cannot excrete phosphorus, leading to hypocalcemia and hyperphosphatemia.
Which of the following thyroid function assay results would you expect with hyperthyroidism? High TSH, low free T4 Normal TSH, normal free T4 Low TSH, high free T4 High TSH, normal free T4
The most useful test for assessing thyroid function is the TSH (thyroid-stimulating hormone). Because more than 99.9% of thyroid hormone is protein-bound, alteration in thyroid hormone-binding proteins frequently leads to total T4 and T3 levels outside of the normal range without representing true clinical thyroid dysfunction. A low TSH and a high free T4 are associated with hyperthyroidism. A high TSH and a low free T4 are associated with primary hypothyroidism. A normal TSH and a normal free T4 would be found in a normal patient. A high TSH and a normal free T4 are associated with subclinical hypothyroidism.
Serum TSH levels five times the upper limit of normal in the presence of a low T4 and low T3 uptake could mean which of the following? The thyroid has been established as the cause of hypothyroidism. The thyroid is ruled out as the cause of hypothyroidism. The pituitary has been established as the cause of hypothyroidism. The diagnosis is consistent with secondary hyperthyroidism.
The thyroid has been established as the cause of hypothyroidism. During primary hypothyroidism, where a defect in the thyroid gland is producing low levels of T3 and T4, the TSH level is increased. TSH is released in elevated quantities in an attempt to stimulate the thyroid to produce more T3 and T4 as part of a feedback mechanism. Primary hypothyroidism can occur extrinsically, due to conditions such as iodine deficiency, or intrinsically due to conditions such as Hashimoto thyroiditis. Secondary hypothyroidism happens due to pituitary or hypothalamic disease and/or disorder.
Circulating organic iodine is found primarily in the form of: Triiodothyronine Parathyroid hormone Thyroglobulin Thyroxine
Thyroxine
All of the following statements about fluorometry are true, EXCEPT: Fluorometry is more sensitive than spectrophotometry. Both excitation and emission spectra are characteristics of the analyte. Fluorescence is indirectly proportional to the analyte being measured. Fluorometers typically utilize monochromators or optical filters.
fluorescence is indirectly proportional to the analyte being measured. A fluorometer generates the wavelength of light required to excite the analyte (fluorophore) of interest; it selectively transmits the wavelength of light emitted, then it measures the intensity of the emitted light. The emitted light is proportional to the concentration of the analyte (fluorophore) being measured (up to a maximum concentration). Monochromators or optical filters help to select the proper excitation and emission wavelengths for the testing being performed.
Deficiency in Vitamin E (fat-soluble) is associated with:
hemolytic anemia (newborn) blood cell fragility, loss of body movement
Deficiency in Vitamin K (fat-soluble) is associated with:
hemorrhage (easy to massive bruising), post traumatic bleeding
Deficiency in Vitamin A (fat-soluble) is associated with:
night blindness, abnormal taste, dermatitis
The testing method for Vitamin K is:
prothrombin time - used as a functional indicator of vitamin K status.