a chemical transmitter substance produced by cells of the body and transported by the bloodstream to the cells and organs on which it has a specific regulatory effect. adj., adj
hormo´nal. Hormones act as chemical messengers to body organs, stimulating certain life processes and retarding others. Growth, reproduction, control of metabolic processes, sexual attributes, and even mental conditions and personality traits are dependent on hormones.
Hormones are produced by various organs and body tissues, but mainly by the endocrine glands
, such as the pituitary, thyroid, and gonads (testes and ovaries). Each gland apparently synthesizes several kinds of hormones; the adrenal glands alone produce more than 25 varieties. The total number of hormones is still unknown, but each has its unique function and its own chemical formula. After a hormone is discharged by its parent gland into the capillaries or the lymph, it may travel a circuitous path through the bloodstream to exert influence on cells, tissues, and organs (target organs) far removed from its site of origin.
One of the best-known endocrine hormones is insulin
, a protein manufactured by the beta cells of the islands of Langerhans in the pancreas that is important in carbohydrate metabolism. Other important hormones are thyroxine
, an iodine-carrying amino acid produced by the thyroid gland; cortisone
, a member of the steroid family from the adrenal glands; and the sex hormones, estrogen
from the ovaries and androgen
from the testes. Certain hormone substances can be synthesized in the laboratory for treatment of human disease. Animal hormones can also be used, as endocrine hormones are to some extent interchangeable among species. Extracts from the pancreas of cattle, for example, enabled diabetes sufferers to live normal lives even before the chemistry of insulin was fully understood.
Endocrine hormone synthesis and secretion is controlled and regulated by a closed-loop system. Negative feedback
loops maintain optimal levels of each hormone in the body. If there are abnormally high levels of a hormone in the blood, feedback to the gland responsible for its production inhibits secretion. If there are abnormally low levels, the gland is stimulated to step up production and secretion. In this way a homeostatic balance is maintained. (See also endocrine glands
adrenocortical hormone 1.
any of the corticosteroids secreted by the adrenal cortex
, the major ones being the glucocorticoids and mineralocorticoids, and including some androgens, progesterone, and estrogens.
(CRH) a neuropeptide secreted by the median eminence of the hypothalamus that binds to specific receptors on the corticotroph cells of the anterior pituitary and stimulates the secretion of corticotropin
ectopic h's those secreted by tumors of nonendocrine tissues but having the same physiologic effects as their normally produced counterparts. It is not known exactly how the synthesis and secretion of endocrine hormones from nonendocrine tissues occurs. Most of these tumors are derived from tissues that have a common embryonic origin with endocrine tissues. When the cells undergo neoplastic transformation, they can revert to a more primitive stage of development and begin to synthesize hormones.
Ectopic hormones present serious problems for patients and add to the complexity of caring for those with certain kinds of neoplastic diseases. These hormones do not respond to the feedback mechanisms that regulate normal hormonal production; hence, surgery and destruction of the tumorous tissue by radiation and chemotherapy are the treatments of choice.
(FSH) one of the gonadotropins
of the anterior pituitary, which stimulates the growth and maturity of graafian follicles in the ovary, and stimulates spermatogenesis in the male.
growth hormone–releasing hormone
(GH-RH) a neuropeptide elaborated by the median eminence of the hypothalamus that binds to specific receptors on the somatotroph cells of the anterior pituitary and stimulates the secretion of growth hormone
a substance with hormone like properties that acts at an anatomically restricted site; most are rapidly degraded. Called also autacoid
(LH) a gonadotropin
of the anterior pituitary gland, acting with follicle-stimulating hormone
to cause ovulation of mature follicles and secretion of estrogen by thecal and granulosa cells of the ovary; it is also concerned with corpus luteum formation. In the male, it stimulates development of the interstitial cells of the testes and their secretion of testosterone. Called also interstitial cell–stimulating hormone
(MSH) a substance from the anterior pituitary gland
of certain other animals but not humans; it influences the formation or deposition of melanin
in the body and pigmentation of the skin.
(PTH) a polypeptide hormone secreted by the parathyroid glands
that influences calcium and phosphorus metabolism and bone formation.
hormones secreted by the placenta, including chorionic gonadotropin
, and other substances having estrogenic, progestational, or adrenocorticoid activity.
2. progestational agent.
a hormone released by the hypothalamus
that inhibits the secretion of prolactin
by the anterior pituitary gland
(TRH) a tripeptide hormone of the hypothalamus, which stimulates release of thyrotropin
from the pituitary gland. In humans, it also acts as a prolactinreleasing factor
. It is used in the diagnosis of mild hyperthyroidism
and Graves disease, and in differentiating between primary, secondary, and tertiary hypothyroidism
hormone (hor'mon?) [Gr. horman, to excite, urge on]
1. A substance originating in an organ, gland, or body part, conveyed through the blood to another body part, and chemically stimulating that part to increase or decrease functional activity or to increase or decrease secretion of another hormone.
The secretion of the ductless glands, e.g., insulin from the pancreas. See: endocrine glandhormonal
adrenocortical hormone Abbreviation: ACH
A hormone (such as aldosterone or cortisol) secreted by the cortex of the adrenal gland. Synonym: cortical hormone See: adrenal gland
adrenocorticotropic hormone Abbreviation: ACTH
A hormone that is secreted by the anterior lobe of the pituitary gland and controls the development and functioning of the adrenal cortex, including its secretion of glucocorticoids and androgens. Synonym: corticotropin
Any of several hormones (such as epinephrine and norepinephrine) produced by the adrenal medulla.
anterior pituitary hormone
Any of several hormones secreted by the anterior lobe of the pituitary, including corticotropin, follicle-stimulating hormone, gonadotropin, growth hormone, luteinizing hormone, melanocyte-stimulating hormone, prolactin, and thyrotropin.
antidiuretic hormone Abbreviation: ADH
A peptide hormone that plays a crucial role in limiting the amount of water excreted by the kidneys. Deficiency of ADH causes central diabetes insipidus, excess causes water retention and hyponatremia. Synonym: vasopressin
ADH is produced by the hypothalamus and stored in the posterior pituitary gland; it is secreted when the osmolarity of plasma rises. Secretion of ADH increases the concentration of the urine by preventing water losses from the renal tubules. ADH also causes constriction of arterioles (raising blood pressure) and increases levels of clotting factor VIII. ADH can be administered to patients in cardiac arrest as an alternative to epinephrine.
atrial natriuretic hormoneAtrial natriuretic factor.
bioidentical natural hormoneBioidentical synthetic hormone.
bioidentical synthetic hormone Abbreviation: BSH
A compound extracted from plants or formulated in the laboratory and used to replace or increase concentrations of hormones found in the body. The most commonly manufactured and marketed BSHs are the sex steroid hormones (estrogen, progesterone, and testosterone). Synonym: bioidentical natural hormone
corpus luteum hormoneProgesterone.
cortical hormoneAdrenocortical hormone.
corticotropin-releasing hormone Abbreviation: CRH
A hormone that is released from the hypothalamus and acts on the anterior pituitary to increase secretion of adrenal corticotropin hormone. In response to stress, CRH causes hyperglycemia, increased oxygen consumption, increased cardiac output, and decreased sexual activity; suppresses release of growth hormone; diminishes gastrointestinal function; stimulates respiration; and causes behavioral changes. Synonym: corticotropin-releasing factor
Any of the hormones that oppose the effects of insulin. They include glucagon, epinephrine, norepinephrine, cortisol, and growth hormone.
Any of a group of hormones produced by the stomach or small intestinal mucosa and stimulating various tissues to release enzymes, produce fluids, or affect gastrointestinal motility. They include gastrin, motilin, secretin, cholecystokinin, and vasoactive intestinal peptide.
follicle-stimulating hormone Abbreviation: FSH
A hormone that is secreted by the anterior lobe of the pituitary and stimulates maturation of the ovarian follicles in women. In men, the hormone is important in maintaining spermatogenesis.
follicle-stimulating hormone releasing hormone Abbreviation: FSH-RH
A hormone from the hypothalamus that regulates release of follicle-stimulating hormone.
gonadotropic hormone, gonadotrophic hormoneGonadotropin.
gonadotropin-releasing hormone Abbreviation: Gn-RH
The hormone produced in the hypothalamus that causes the pituitary to release luteinizing hormone and follicle-stimulating hormone. This hormone is used in treating endometriosis. Synonym: luteinizing hormone-releasing hormone
growth hormone Abbreviation: GH
A hormone secreted by the anterior pituitary and regulating the cell division and protein synthesis necessary for normal growth. It is a protein made from a single chain of amino acids; molecular weight 22 kDa. Synonym: somatotropin
growth hormone-releasing hormone Abbreviation: GH-RH
A hormone from the hypothalamus that stimulates the release of growth hormone. Synonym: somatotropin-releasing hormone
human growth hormone Abbreviation: HGH
See: growth hormone
human placental lactogen hormone See: human placental lactogen
A hormone that influences components of the immune system, including the number and activity of the white blood cells. Such hormones are secreted by almost all of the glands in the body, particularly the hypothalamus and adrenal glands.
Any of a group of substances limiting the release of hormones from the pituitary. Somatostatin, which inhibits the release of growth hormone, is included in this group.
interstitial cell-stimulating hormone Abbreviation: ICSH
An obsolete term for luteinizing hormone.
Any of several hormones produced by the mucosa of the intestine. They include cholecystokinin, motilin, secretin, and vasoactive inhibitory peptide.
Any hormone (such as epinephrine, glucagon, and cortisol) that promotes release of free fatty acids from fat tissue.
luteinizing hormone Abbreviation: LH
A hormone produced by the anterior lobe of the pituitary, in females stimulating the development of the corpus luteum and helping in the secretion of progesterone, and in males stimulating the development of interstitial cells of the testes to produce testosterone. Synonym: luteotropic hormone
luteinizing hormone-releasing hormone Abbreviation: LH-RH
luteotropic hormone Abbreviation: LTH
melanocyte-stimulating hormone Abbreviation: MSH
A hormone of the anterior pituitary gland that causes pigmentation of the skin in humans. Synonym: intermedin
A hormone produced by the ovary. See: estradiol; estriol; estrogen; estrone; progesterone
A hormone produced by the islets of Langerhans of the pancreas. See: glucagon; insulin
parathyroid hormone Abbreviation: PTH
A hormone secreted by the parathyroid glands that regulates blood levels of calcium and phosphorus. A deficiency results in hypoparathyroidism and hypocalcemia; in excess, it causes hyperparathyroidism and hypercalcemia. Synonym: parathormone
Any of the hormones secreted by the placenta, including estrogen, progesterone, and human chorionic gonadotropin.
posterior pituitary hormone
Any of the hormones secreted by the posterior lobe of the pituitary (such as vasopressin and oxytocin). See: antidiuretic hormone
releasing hormone Abbreviation: RH
Any of a group of substances secreted by the hypothalamus that control or inhibit the release of various hormones. They include thyrotropin-releasing hormone, gonadotropin-releasing hormone, dopamine, growth hormone-releasing hormone, corticotropin-releasing hormone, and somatostatin. Dopamine and somatostatin act to inhibit release of the hormones they act upon.
An androgen or an estrogen.
somatotropic hormone Abbreviation: STH
somatotropin-releasing hormoneGrowth hormone-releasing hormone.
One of the sex hormones and hormones of the adrenal cortex.
synthetic human growth hormone
A growth hormone made with recombinant DNA techniques.
A hormone produced by the interstitial tissue of the testis (such as testosterone and inhibin).
Any of the hormones produced by the thymus that may help attract lymphoid stem cells to the thymus and stimulate their development into mature T lymphocytes. They include thymulin, thymopoietin, and thymosin.
Either of two hormones, thyroxine (T4) or triiodothyronine (T3, secreted by the follicles of the thyroid gland. They act on receptors in tissues throughout the body to increase the production of cellular proteins, the metabolic rate, and the activities of the sympathetic nervous system. Deficiency of thyroid hormone produces clinical hypothyroidism; excess causes hyperthyroidism.
thyroid-stimulating hormone Abbreviation: TSH
thyrotropin-releasing hormone Abbreviation: TRH
A hormone secreted by the hypothalamus that stimulates the anterior pituitary to release thyrotropin. It was formerly called thyroid-stimulating hormone-releasing factor.
A hormone secreted by one gland (e.g. the pituitary gland) that stimulates another gland to secrete its hormone or hormones.