Chapter 16: Endocrine System

Function

The endocrine system regulates body activities through the use of chemical messengers called hormones, which when released into the bloodstream influence metabolic activities, growth, and development (Fig. 16.1). The nervous system also regulates body activities by receiving electrical impulses that convey information about the state of the body, and then activating glandular secretions in response. Hormones secreted by the endocrine glands that make up the endocrine system go directly into the bloodstream and are transported throughout the body. They are referred to as ductless glands because they do not have ducts to carry their secretions. In contrast, the exocrine or duct glands have ducts that carry their secretions from the producing gland to other parts of the body. An example is the parotid gland, which produces saliva that flows through the parotid duct into the mouth. Only those terms related to the major endocrine glands—pituitary, thyroid, parathyroids, adrenals, and the islets of Langerhans in the pancreas—are presented in this chapter. The thymus primarily functions as part of the lymphatic system and was presented in Chapter 10. The male and female sex glands were also presented in previous chapters. pg 637

Characteristics

abrupt onset, occurs primarily in childhood or adolescence; patients often are thin

Combining Forms of the Endocrine System adren/o, adrenal/o

adrenal glands

Endocrine Glands and Hormones pituitary gland (pi-TOO-i-tar-ē) (gland)

approximately the size of a pea and located at the base of the brain. The pituitary is divided into two lobes. It is often referred to as the master gland because it produces hormones that stimulate the function of other endocrine glands (also called hypophysis cerebri) (Fig. 16.2).

Gigantism and Acromegaly

are both caused by overproduction of growth hormone. Gigantism occurs before puberty and before the growing ends of the bones have closed. If untreated, an individual may reach 8 feet tall in adulthood. Acromegaly occurs after puberty. The body parts most affected are those in the hands, feet, and jaw.

TYPE 1 DIABETES MELLITUS Cause

autoimmune disease in which the beta cells of the pancreas that produce insulin are destroyed and eventually no insulin is produced

Graves disease (grāvz) (di-ZĒZ)

autoimmune disorder of the thyroid gland characterized by the production of more thyroid hormone than the body needs (hyperthyroidism), goiter, and exophthalmos (abnormal protrusion of the eyeballs)

fine needle aspiration (FNA) (FĪN) (NĒ-del) (as-pi-RĀ-shen)

biopsy technique that uses a narrow hollow needle to obtain tiny amounts of tissue for pathologic examination. Thyroid nodules are frequently biopsied using FNA

thyroxine level (T4) (thī-ROK-sin) (LEV-el)

blood test that gives the direct measurement of the amount of thyroxine in the patient's blood. A greater-than-normal amount indicates hyperthyroidism; a less-than-normal amount indicates hypothyroidism

thyroid-stimulating hormone level (TSH) (THĪ-royd) (STIM-yuh-lāt-ing) (HŌR-mōn) (LEV-el)

blood test that measures the amount of thyroid-stimulating hormone in the blood; used to diagnose hypothyroidism and to monitor patients on thyroid replacement therapy

LABORATORY fasting blood sugar (FBS) (FAST-ing) (blud) (SHOOG-er)

blood test to determine the amount of glucose (sugar) in the blood after fasting for 8-10 hours. Elevation may indicate diabetes mellitus

glycosylated hemoglobin (HbA1C) (glī-KŌ-sa-lāt-ad) (HĒ-mō-glō-bin)

blood test used to diagnose diabetes and monitor its treatment by measuring the amount of glucose (sugar) bound to hemoglobin in the blood. HbA1C provides an indication of blood sugar level over the past three months, covering the 120-day lifespan of the red blood cell (also called glycated hemoglobin, hemoglobin A1C, and A1C test).

calc/i

calcium (Note: the combining vowel is i.)

diabetes mellitus (DM) (dī-a-BĒ-tēz) (MEL-li-tus)

chronic disease involving a disorder of carbohydrate metabolism caused by under-activity of the insulin-producing islets of Langerhans and characterized by elevated blood sugar (hyperglycemia). DM can cause chronic renal disease, retinopathy, and neuropathy. In extreme cases the patient may develop ketosis, acidosis, and finally coma. (Table 16.1)

Addison disease (AD-i-sun) (di-ZĒZ)

chronic syndrome resulting from a deficiency in the hormonal secretion of the adrenal cortex. Signs and symptoms may include weakness, weight loss, hypotension, darkening of skin, and loss of appetite

islets of Langerhans (Ī-lets) (LAHNG-er-hahnz

clusters of endocrine tissue found throughout the pancreas, made up of different cell types that secrete various hormones, including insulin and glucagon. Non-endocrine cells found throughout the pancreas produce enzymes that facilitate digestion (Fig. 16.4).

tetany (TET-a-nē)

condition affecting nerves causing muscle spasms as a result of low amounts of calcium in the blood caused by a deficiency of the parathyroid hormone

gigantism (jī-GAN-tizm)

condition brought about by hypersecretion of growth hormone by the pituitary gland before puberty

congenital hypothyroidism (kon-JEN-i-tal) (hī-pō-THĪ-royd-izm)

condition caused by congenital absence or atrophy (wasting away) of the thyroid gland, resulting in hypothyroidism. The disease is characterized by puffy features, mental deficiency, large tongue, and dwarfism.

thyrotoxicosis (thī-rō-tok-si-KŌ-sis)

condition caused by excessive thyroid hormones

myxedema (mik-se-DĒ-ma)

condition resulting from an extreme deficiency of the thyroid hormone thyroxine; a severe form of hypothyroidism in an adult. Signs include puffiness of the face and hands, coarse and thickened skin, enlarged tongue, slow speech, and anemia

LONG-TERM COMPLICATIONS OF DIABETES MELLITUS MACROVASCULAR COMPLICATIONS

coronary artery disease → myocardial infarction cerebrovascular disease → stroke peripheral artery disease → leg pain when walking (intermittent vascular claudication)

cortic/o

cortex (the outer layer of a body organ

hypocalcemia (hī-pō-kal-SĒ-mē-a)

deficient calcium in the blood

hypokalemia (hī-pō-ka-LĒ-mē-a)

deficient potassium in the blood

hyponatremia (hī-pō-na-TRĒ-mē-a)

deficient sodium in the blood

hypoglycemia (hī-pō-glī-SĒ-mē-a)

deficient sugar in the blood

MICROVASCULAR COMPLICATIONS

diabetic retinopathy → loss of vision diabetic nephropathy → chronic renal disease, kidney failure neuropathy → loss of feeling in the distal extremities (feet, hands), which can lead to amputation

Treatment

diet, exercise, oral or injected medication, and sometimes insulin

adrenopathy (ad-ren-OP-a-thē)

disease of the adrenal gland

endocrin/o

endocrine

adrenomegaly (a-drē-nō-MEG-a-lē)

enlargement (of one or both) of the adrenal glands

Disease and Disorder Terms Built From Word Parts acromegaly (ak-rō-MEG-a-lē)

enlargement of the extremities (and face due to increased soft tissue, bone, and cartilage; caused by excessive production of the growth hormone by the pituitary gland after puberty) (Exercise Figure A)

goiter (GOY-ter)

enlargement of the thyroid gland. May be caused by autoimmune diseases of the thyroid (Graves disease or Hashimoto thyroiditis), iodine deficiency, or the presence of multiple nodules.

hypercalcemia (hī-per-kal-SĒ-mē-a

excessive calcium in the blood

Complementary Terms Built From Word Parts adrenocorticohyperplasia (a-drē-nō-kōr-ti-kō-hī-per-PLĀ-zha)

excessive development of the adrenal cortex (Note: hyper, a prefix, appears within this term.)

hyperkalemia (hī-per-ka-LĒ-mē-a)

excessive potassium in the blood

hyperglycemia (hī-per-glī-SĒ-mē-a)

excessive sugar in the blood

Surgical Terms Built From Word Parts adrenalectomy (ad-rē-nal-EK-to-mē)

excision of (one or both) adrenal glands

parathyroidectomy (par-a-thī-royd-EK-to-mē

excision of (one or more) parathyroid glands

pancreatectomy (pan-crē-a-TEK-ta-mē)

excision of the pancreas

thyroidectomy (thī-royd-EK-to-mē)

excision of the thyroid gland

Combining Forms Commonly Used with Endocrine System Terms acr/o

extremities, height

Signs and Symptoms

fatigue, blurred vision, thirst, and hyperglycemia; these may be present if blood sugar is not controlled

parathyroid glands (par-a-THĪ-royd) (glans

four small bodies embedded in the posterior aspect of the lobes of the thyroid gland (Fig. 16.3D). Parathyroid hormone (PTH), the hormone produced by the glands, helps maintain the level of calcium in the blood by its effects on bone and kidneys.

metabolic syndrome (met-a-BOL-ik) (SIN-drōm)

group of signs and symptoms including insulin resistance, obesity characterized by excessive fat around the area of the waist and abdomen, hypertension, hyperglycemia, elevated triglycerides, and low levels of the "good" cholesterol HDL. Risks include development of type 2 diabetes mellitus, coronary heart disease, or stroke (also called syndrome X and insulin resistance syndrome).

adrenalitis (a-drē-nal-Ī-tis)

inflammation of the adrenal glands

thyroiditis (thī-royd-Ī-tis)

inflammation of the thyroid gland

Treatment

insulin injections and diet

Integrative Medicine Term Yoga

is the practice of physical postures, conscious breathing, and meditation. Studies have revealed the regular practice of yoga demonstrates efficacy as an adjunct therapy for management of type 2 diabetes mellitus, may promote healthy aging by maintaining the basal levels of growth hormone and DHEA, supports regulation of several reproductive hormones, and contributes to the improvement of psycho-physical health when under stress.

Hypothyroidism

is the state of deficient thyroid gland activity, resulting in the decreased production of the thyroid hormone called thyroxine. A severe form of hypothyroidism in adults is called myxedema and in infants is called congenital hypothyroidism.

thyroid gland (THĪ-royd) (gland)

largest endocrine gland. It is located anteriorly in the neck below the larynx and comprises bilateral lobes connected by an isthmus (Fig. 16.3C). The thyroid gland secretes the hormones triiodothyronine (T3) and thyroxine (T4), which require iodine for their production. Thyroxine is necessary for body cell metabolism.

hypothalamus (hī-pō-THAL-a-mus)

located superior to the pituitary gland in the brain. The hypothalamus secretes "releasing" hormones that function to stimulate or inhibit the release of pituitary gland hormones.

sestamibi parathyroid scan (ses-ta-MIB-ē) (par-a-THĪ-royd) (skan)

nuclear medicine procedure used to localize hyperactive parathyroid glands. The glands that take up an abnormal amount of radioactive substance are identified and selected for surgical removal; the other parathyroid glands may be left in place.

Diagnostic Terms Not Built From Word Parts DIAGNOSTIC IMAGING radioactive iodine uptake (RAIU) (rā-dē-ō-AK-tiv) (Ī-ō-dīn) (UP-tāk)

nuclear medicine scan that measures thyroid function, particularly when distinguishing different causes of hyperthyroidism. Radioactive iodine is given to the patient orally, after which the amount of its uptake into the thyroid gland is measured. Images of the gland can also be obtained using this procedure

adrenal glands (a-DRĒ-nal) (glans)

paired glands, one of which is located superior to each kidney. The outer portion is called the adrenal cortex, and the inner portion is called the adrenal medulla. The following hormones are secreted by the adrenal glands

parathyroid/o

parathyroid glands

cortical (KŌR-ti-kal)

pertaining to the cortex

endocrinologist (en-dō-kri-NOL-o-jist)

physician who studies and treats diseases of the endocrine (system

pituitar/o

pituitary gland

Signs and Symptoms

polyuria, polydipsia, weight loss, and hyperglycemia; these are present if blood sugar is not controlled, and can progress to ketoacidosis if not promptly treated

kal/i

potassium (Note: the combining vowel is i.)

anterior lobe (ān-TĒR-ē-er) (lōb

produces and secretes the following hormones (also called adenohypophysis):

prolactin (PRL) (prō-LAK-tin)

promotes development of glandular tissue during pregnancy and produces milk after birth of an infant

growth hormone (GH) (grohth) (HŌR-mōn)

regulates the growth of the body

corticoid (KŌR-ti-koyd)

resembling the cortex

TYPE 2 DIABETES MELLITUS Cause

resistance of body cells to the action of insulin, coupled with a decrease in the ability of the pancreas to make sufficient insulin to overcome this resistance

diabetes insipidus (DI) (dī-a-BĒ-tēz) (in-SIP-i-dus)

result of decreased secretion of antidiuretic hormone by the posterior lobe of the pituitary gland. Symptoms include excessive thirst (polydipsia), large amounts of urine (polyuria), and water being excreted from the body.

aldosterone (al-DOS-ter-ōn)

secreted by the adrenal cortex. Electrolytes (mineral salts) that are necessary for normal body function are regulated by this hormone

cortisol (KOR-ti-sol)

secreted by the adrenal cortex. It aids the body during stress by increasing glucose levels to provide energy (also called hydrocortisone).

epinephrine, norepinephrine (ep-i-NEF-rin), (nor-ep-i-NEF-rin)

secreted by the adrenal medulla. These hormones help the body to deal with stress by increasing the blood pressure, heartbeat, and respirations. (also called adrenaline and noradrenaline, respectively)

ketoacidosis (kē-tō-as-i-DŌ-sis

serious condition resulting from uncontrolled diabetes mellitus in which acid ketones accumulate from fat metabolism in the absence of adequate insulin. If not promptly controlled by adequate insulin and hydration, can progress to coma and death

Characteristics

slow onset, usually occurs in middle-aged or elderly adults; most patients are obese

natr/o

sodium

hypopituitarism (hī-pō-pi-TŪ-i-ta-rizm)

state of deficient pituitary gland activity (characterized by decreased secretion of one or more of the pituitary hormones, which can affect the function of the target endocrine gland; for example, hypothyroidism can result from decreased secretion of thyroid-stimulating hormone by the pituitary gland

hypothyroidism (hī-pō-THĪ-royd-izm)

state of deficient thyroid gland activity (characterized by decreased secretion of thyroid hormones. Signs and symptoms include fatigue, weight gain, and cold intolerance.)

hyperparathyroidism (hī-per-par-a-THĪ-royd-izm

state of excessive parathyroid gland activity (resulting in hypercalcemia and leading to osteoporosis, as well as symptoms of muscle weakness, abdominal pain, nausea, vomiting, and drowsiness)

hyperpituitarism (hī-per-pi-TOO-i-ta-rizm)

state of excessive pituitary gland activity (characterized by excessive secretion of pituitary hormones)

hyperthyroidism (hī-per-THĪ-royd-izm)

state of excessive thyroid gland activity (characterized by excessive secretion of thyroid hormones. Signs and symptoms include weight loss, irritability, and heat intolerance.)

panhypopituitarism (pan-hī-pō-pi-TŪ-i-ta-rizm)

state of total deficient pituitary gland activity (characterized by decreased secretion of all the anterior pituitary hormones; this is a more serious condition than hypopituitarism in that it affects the function of all the other endocrine glands) (Note: two prefixes are contained in this term)

gonadotropic hormones (gō-na-dō-TRŌ-pik) (HŌR-mōns)

stimulate the gonads (the testes in males and ovaries in females). Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are the gonadotropic hormones released from the adenohypophysis

adrenocorticotropic hormone (ACTH) (a-drē-nō-kōr-ti-kō-TRŌ-pik) (HŌR-mōn)

stimulates the adrenal cortex

antidiuretic hormone (ADH) (an-tē-dī-ū-RET-ik) (HŌR-mōn)

stimulates the kidney to reabsorb water and constricts blood vessels to help maintain blood pressure (also called vasopressin)

thyroid-stimulating hormone (TSH) (THĪ-royd) (STIM-yuh-lāt-ing) (HŌR-mōn)

stimulates the thyroid gland

oxytocin (ok-sē-TŌ-sin)

stimulates uterine contractions during labor and postpartum, and milk let down by the breasts postpartum

posterior lobe (po-STĒR-ē-er) (lōb)

stores and releases antidiuretic hormone and oxytocin (also called neurohypophysis)

dips/o

thirst

thyr/o, thyroid/o

thyroid gland

parathyroidoma (par-a-thī-royd-Ō-ma)

tumor of a parathyroid gland

pheochromocytoma (fē-ō-krō-mō-sī-TŌ-ma

tumor of the adrenal medulla, which is usually non-malignant and characterized by hypertension, headaches, palpitations, diaphoresis, chest pain, and abdominal pain. Surgical removal of the tumor is the most common treatment. Though usually curable with early detection, it can be fatal if untreated

thyroid sonography (THĪ-royd) (so-nog-ra-fē)

ultrasound test of the thyroid gland used to help determine whether a thyroid nodule is likely benign or possibly malignant, including whether it is cystic or solid. Also used to help guide a fine needle aspiration (FNA) biopsy.

Cushing Syndrome (KŪSH-ing) (SIN-drōm)

was named for an American neurosurgeon, Harvey Williams Cushing (1869-1939), after he described adrenocortical hyperfunction group of signs and symptoms attributed to the excessive production of cortisol by the adrenal cortices (pl. of cortex). This syndrome may be the result of a pituitary tumor that produces ACTH or a primary adrenal cortex hypersecretion. Signs include abnormally pigmented skin, "moon face," pads of fat on the chest and abdomen, "buffalo hump" (fat on the upper back), wasting away of muscle, and hypertension

Disease and Disorder Terms Not Built From Word Parts Addison Disease

was named in 1855 for Thomas Addison, an English physician and pathologist. He described the disease as a "morbid state with feeble heart action, anemia, irritability of the stomach, and a peculiar change in the color of the skin."