Endocrine System

adrenal gland

a gland on the superior surface of the kidney; the outer region (cortex) secretes steroid hormones; the inner region (medulla) secretes epinephrine (adrenaline) in response to stress

endocrine

pertaining to a ductless gland that secretes hormones into the blood

hormone

a secretion of an endocrine gland; a substance that travels in the blood and has a regulatory effect on tissues, organs, or glands

hypophysis

the pituitary gland; named from hypo, meaning “below,” and physis, meaning “growing,” because the gland develops below the hypothalamus

hypothalamus

a portion of the brain that controls the pituitary gland, produces hormones, and is active in maintaining homeostasis

pancreatic islet

cluster of endocrine cells in the pancreas that secretes hormones to regulate glucose metabolism; also called islet of Langerhans or islet cells

parathyroid gland

a small endocrine gland on the posterior thyroid that acts to increase blood calcium levels; there are usually four to six parathyroid glands (roots: parathyr/o, parathyroid/o); the name literally means “near the thyroid”

pineal gland

a small gland in the brain; appears to regulate mood, daily rhythms, and sexual development in response to environmental light; secretes the hormone melatonin

pituitary gland

a small endocrine gland at the base of the brain; the anterior lobe secretes growth hormone and hormones that stimulate other glands; the posterior lobe releases ADH and oxytocin manufactured in the hypothalamus

prostaglandins

a group of hormones produced throughout the body that have a variety of effects, including stimulation of uterine contractions and regulation of blood pressure, blood clotting, and inflammation

receptor

a site on the cell membrane or within the cell to which a substance, such as a hormone, attaches

steroid hormone

a hormone made from lipids; includes the sex hormones and the hormones of the adrenal cortex

target tissue

the specific tissue on which a hormone acts; may also be called the target organ

thyroid gland

an endocrine gland on either side of the larynx and upper trachea; it secretes hormones that affect metabolism and growth

acromegaly

overgrowth of bone and soft tissue, especially in the hands, feet, and face, caused by excess growth hormone in an adult; the name comes from acro meaning “extremity” and megal/o meaning “enlargement”

Addison disease

a disease resulting from deficiency of adrenocortical hormones; it is marked by darkening of the skin, weakness, and alterations in salt and water balance

adenoma

a neoplasm of a gland

adult hypothyroidism

a condition caused by hypothyroidism in an adult; there is dry, waxy swelling, most notable in the face; formerly called myxedema

congenital hypothyroidism

a condition caused by lack of thyroid secretion during development and marked by arrested physical and mental growth; also called infantile hypothyroidism

Cushing disease

Overactivity of the adrenal cortex resulting from excess production of ACTH by the pituitary

Cushing syndrome

a condition resulting from an excess of hormones from the adrenal cortex; it is associated with obesity, weakness, hyperglycemia, hypertension, and hirsutism

diabetes insipidus

a disorder caused by insufficient release of ADH from the posterior pituitary; it results in excessive thirst and production of large amounts of very dilute urine; insipidus means “tasteless,” referring to the dilution of the urine

diabetes mellitus (DM)

a disorder of glucose metabolism caused by deficiency of insulin production or inadequate tissue response to insulin; type 1 results from autoimmune destruction of pancreatic islet cells; it generally appears in children and requires insulin administration; type 2 generally occurs in obese adults; it is treated with diet, exercise, and drugs to improve insulin production or activity, and sometimes insulin; mellitus comes from the Latin root for honey, referring to the urine’s glucose content

exophthalmos

protrusion of the eyeballs, as seen in Graves disease

gigantism

overgrowth caused by excess growth hormone from the pituitary during childhood

glycated hemoglobin (HbA1c) test

a test that measures the binding of glucose to hemoglobin during the lifespan of a red blood cell; it reflects the average blood glucose level over 2 to 3 months and is useful in evaluating long-term therapy for diabetes mellitus; also called A1c test

glycosuria

excess glucose in the urine

goiter

enlargement of the thyroid gland; a simple (nontoxic) goiter is caused by iodine deficiency

Graves disease

An autoimmune disease resulting in hyperthyroidism; a prominent symptom is exophthalmos (protrusion of the eyeballs); also called diffuse toxic goiter

hyperglycemia

excess glucose in the blood

hypoglycemia

abnormally low level of glucose in the blood

insulin shock

a condition resulting from an overdose of insulin, causing hypoglycemia

ketoacidosis

acidosis (increased acidity of body fluids) caused by excess ketone bodies, as in diabetes mellitus; diabetic acidosis

metabolic syndrome

a state of hyperglycemia caused by cellular resistance to insulin, as seen in type 2 diabetes, in association with other metabolic disorders; also called syndrome X or insulin resistance syndrome

panhypopituitarism

underactivity of the entire pituitary gland

tetany

irritability and spasms of muscles; may be caused by low blood calcium and other factors

sella turcica

a saddle-shaped depression in the sphenoid bone that contains the pituitary gland

sphenoid bone

a bone at the base of the skull that houses the pituitary gland

adrenogenital syndrome

condition caused by overproduction of androgens from the adrenal cortex, resulting in masculinization; may be congenital or acquired, usually as a result of an adrenal tumor

Conn syndrome

hyperaldosteronism caused by an adrenal tumor

craniopharyngioma

a benign tumor of the pituitary gland

Hashimoto disease

a chronic thyroiditis of autoimmune origin

impaired glucose tolerance (IGT)

high blood glucose levels after glucose intake that may signal borderline diabetes mellitus

ketosis

accumulation of ketone bodies, such as acetone, in the body; usually results from deficiency or faulty metabolism of carbohydrates, as in cases of diabetes mellitus and starvation

multiple endocrine neoplasia (MEN)

hereditary disorder that causes tumors in several endocrine glands; classified according to the combination of glands involved

pheochromocytoma

a usually benign tumor of the adrenal medulla or other structures containing chromaffin cells (cells that stain with chromium salts) (phe/o means “brown” or “dusky”); the adrenal tumor causes increased production of epinephrine

pituitary apoplexy

sudden massive hemorrhage and degeneration of the pituitary gland associated with a pituitary tumor; common symptoms include severe headache, visual problems, and loss of consciousness

seasonal affective disorder (SAD)

a mood disorder with lethargy, depression, excessive need for sleep, and overeating that generally occurs in winter; thought to be related to melatonin levels as influenced by environmental light

Simmonds disease

hypofunction of the anterior pituitary (panhypopituitarism), usually because of an infarction; pituitary cachexia

thyroid storm

a sudden onset of thyrotoxicosis symptoms occurring in patients with hyperthyroidism who are untreated or poorly treated; may be brought on by illness or trauma; also called thyroid crisis

thyrotoxicosis

condition resulting from overactivity of the thyroid gland; symptoms include anxiety, irritability, weight loss, and sweating; the main example of thyrotoxicosis is Graves disease

von Recklinghausen disease

bone degeneration caused by excess production of parathyroid hormone; also called Recklinghausen disease of bone

fasting plasma glucose (FPG)

measurement of blood glucose after a fast of at least 8 hours; a reading equal to or greater than 126 mg/dL indicates diabetes; also called fasting blood glucose (FBG) or fasting blood sugar (FBS)

free thyroxine index (FTI, T7)

calculation based on the amount of T4 present and T3 uptake, used to diagnose thyroid dysfunction

oral glucose tolerance test (OGTT

measurement of glucose levels in blood plasma after administration of a challenge dose of glucose to a fasting patient; used to measure patient’s ability to metabolize glucose; a value equal to or greater than 200 mg/dL in the two-hour sample indicates diabetes

radioactive iodine uptake test (RAIU)

a test that measures thyroid uptake of radioactive iodine as an evaluation of thyroid function

radioimmunoassay (RIA)

a method of measuring very small amounts of a substance, especially hormones, in blood plasma using radioactively labeled hormones and specific antibodies

thyroid scan

visualization of the thyroid gland after administration of radioactive iodine

thyroxine-binding globulin (TBG) test

test that measures the main protein that binds T4 in the blood

transsphenoidal adenomectomy

removal of a pituitary tumor through the sphenoid sinus (space in the sphenoid bone)