Endocrinology Practice Flashcards

Vocabulary flashcards covering the major concepts, hormones, and clinical disorders of the endocrine system based on lecture notes.

Hormone

A substance that acts at a site distant from its place of origin; a chemical messenger in the body that produces biochemical changes to increase activity of a process.

Positive feedback mechanism

A process where an increase in the product increases the activity of the system and the production rate.

Negative feedback mechanism

A process where an increase in the product decreases the activity of the system and the production rate.

Autocrine

Hormone action where the substance acts directly upon the cells of origin themselves.

Paracrine

Hormone action where the substance acts adjacent to the cells of origin.

Intracrine

Hormone action where the substance acts within the cells of origin without ever exiting the cells.

Endocrine Action

Hormones secreted in one location, released into blood circulation, and binding to a specific receptor to elicit a physiological response.

Juxtacrine

Hormones secreted in endocrine cells that remain in relation to the plasma membrane and act on immediately adjacent cells by direct cell-to-cell contact.

Neuroendocrine

Hormones secreted in endocrine cells that interact with receptors of cells at a distant site.

Cholesterol

The basic molecule for steroid hormones, which are primarily involved in the regulation of sexual development and characteristics.

Tyrosine

The amino acid precursor for $T4$, $T3$, epinephrine, and norepinephrine.

Prostaglandins

A class of hormones formed from arachidonic acid (fatty acids).

Melatonin

A hormone produced by the pineal gland that regulates the circadian rhythm (sleep-wake cycle).

Tropic Hormones

Hormones that stimulate the activity of other specific endocrine glands.

Direct Effector Hormones

Hormones that exert a direct effect in peripheral tissues.

Somatotropes

Anterior pituitary cells that secrete Growth Hormone ($GH$).

Lactotropes

Anterior pituitary cells that secrete Prolactin ($PRL$).

Thyrotropes

Anterior pituitary cells that secrete Thyroid Stimulating Hormone ($TSH$).

Gonadotropes

Anterior pituitary cells that secrete the alpha and beta subunits of Follicle Stimulating Hormone ($FSH$) and Luteinizing Hormone ($LH$).

Corticotropes

Anterior pituitary cells that secrete proopiomelanocortin ($POMC$), which is cleaved to form Adrenocorticotropin ($ACTH$), beta-endorphin, and beta-lipotropin ($b-LPH$).

Ghrelin

A hormone produced by gastric neuroendocrine cells and the hypothalamus that stimulates the secretion of $GHRH$.

Gigantism

A disorder caused by Growth Hormone excess in children.

Acromegaly

A disorder caused by Growth Hormone excess in adults.

Pituitary Dwarfism

A condition caused by the deficiency of Growth Hormone, leading to subnormal growth.

Insulin Tolerance Test

The gold standard test for diagnosing Growth Hormone Deficiency ($GHD$).

Dopamine

Also known as Prolactin Inhibiting Factor ($PIF$); it is the major inhibitor of prolactin release.

Milk let-down

The main physiological effect of oxytocin.

True Diabetes Insipidus

A condition characterized by a deficiency of $ADH$ with normal $ADH$ receptors, typically due to hypothalamic or pituitary disease.

Nephrogenic Diabetes Insipidus

A condition characterized by normal $ADH$ levels but abnormal $ADH$ receptors, resulting in renal resistance to $ADH$.

SIADH

Syndrome of Inappropriate Antidiuretic Hormone secretion; occurs when there is uncontrolled secretion of $ADH$ without a known stimulus, causing hyponatremia.

Follicular Cells

Cells in the thyroid gland that produce $T3$, $T4$, and $rT3$.

Parafollicular Cells (C cells)

Cells in the thyroid gland that produce Calcitonin.

Thyroglobulin

The prohormone of $T3$; acts as a preformed matrix containing tyrosyl groups synthesized by follicles.

Free T4 ($FT4$)

The nonprotein bound, metabolically active form of thyroxine used to evaluate subclinical hyper/hypothyroidism.

Reverse T3 ($rT3$)

The metabolically inactive product of inner ring deiodination of $T4$, which is increased in euthyroid sick syndrome.

Hashimoto's Thyroiditis

The most common cause of primary hypothyroidism; a chronic autoimmune thyroiditis where $TPOAb$ and $TgAb$ are present.

Graves' Disease

The most common cause of thyrotoxicosis; an autoimmune disorder characterized by a diffuse toxic goiter and the presence of $TRAb$ and $TSI$.

Cretinism

A condition where irreversible neurological and mental deficiency occurs if neonatal hypothyroidism is untreated in the first three months of life.

Thyroid Storm

A life-threatening complication resulting from uncontrolled thyrotoxicosis.

Parathyroid Hormone ($PTH$)

A hypercalcemic hormone whose main role is to prevent hypocalcemia by regulating calcium and phosphate.

Aldosterone

The principal mineralocorticoid synthesized by the zona glomerulosa; promotes water and $Na$ reabsorption in the kidney.

Cortisol

The main glucocorticoid and most abundant adrenal hormone; synthesized in the zona fasciculata to maintain blood glucose and blood pressure.

Porter-Silber Method

A laboratory method used to measure the urine metabolite of cortisol, $17-hydroxycorticosteroid$ ($17-OHCS$), using phenylhydrazine reagent.

Zimmermann Reaction

A laboratory method used to measure $17-Ketosteroids$ and $17-Ketogenic Steroids$ using meta-dinitrobenzene reagent.

Dexamethasone

An exogenous substitute for cortisol used in suppression tests to diagnose Cushing’s syndrome.

Cushing's Syndrome

Primary hypercortisolism characterized by increased serum cortisol, hyperglycemia, weight gain in the face (moon face), and a buffalo humpback.

Addison’s Disease

Primary adrenal insufficiency or hypocortisolism resulting from an autoimmune process or adrenal hypoplasia; symptoms include hypotension and hyperkalemia.

Cosyntropin

A synthetic stimulator of cortisol and aldosterone secretion used in the gold standard $ACTH$ stimulation test.

Conn's Syndrome

Primary hyperaldosteronism characterized by low renin and autonomous over-secretion of aldosterone.

VMA (Vanillylmandelic Acid)

The major urine metabolite of norepinephrine and epinephrine; also known as $HMMA$.

Pheochromocytoma

A tumor of the adrenal medulla or sympathetic ganglia causing extremely elevated blood pressure due to overproduction of catecholamines.

Testosterone

The most potent male androgen, regulated by $FSH$ and $LH$; its primary urinary metabolite is $17-ketosteroids$.

Estrone ($E1$)

The type of estrogen that increases during the menopausal stage.

Estradiol ($E2$)

The most potent estrogen and the dominant form during the reproductive stage; it is cardioprotective and important for coagulation.

Estriol ($E3$)

The type of estrogen that is significantly increased during pregnancy.

Progesterone

A hormone produced by the corpus luteum used to evaluate fertility and maintain pregnancy; its metabolite is $pregnanediol$.

Klinefelter Syndrome

A male sex chromosome abnormality ($47\text{ XXY}$) characterized by decreased testosterone, increase estrogen, gynecomastia, and small testes.

Turner Syndrome

A genetic defect in females characterized by the partial or complete loss of an $X$ chromosome, resulting in nonfunctional ovaries.

Human Chorionic Gonadotropin ($hCG$)

A hormone secreted by syncytiotrophoblast cells that prolongs the viability of the corpus luteum in early pregnancy.

Human Placental Lactogen ($HPL$)

A hormone that reflects the integrity of placental function; levels rise throughout gestation and peak near term.