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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.
See also: hormone
a chemical transmitter substance produced by cells of the body and transported by the bloodstream and other means to the cells and organs which carry specific receptors for the hormone and on which it has a specific regulatory effect.
Hormones act as chemical messengers to body organs, stimulating certain life processes and retarding others. Growth, reproduction, control of metabolic processes, sexual attributes and behavior 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 manufactures 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 structure. 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.
substances secreted by the adrenal medulla, including epinephrine and norepinephrine.
the masculinizing hormones, androstenedione and testosterone.
modern techniques include the use of competitive protein binding assay and radioimmunoassay.
any hormone which is specifically involved in the homeostatic regulation of serum calcium levels through their effects on bone and other organs, e.g. parathyroid hormone, calcitonin.
corpus luteum hormone
those secreted by tumors of nonendocrine tissues but having the same physiological 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.
hormone secreted by endocrine cells in the wall of the intestine or stomach or in the pancreas. Includes gastrin, cholecystokinin, secretin, gastric inhibitory polypeptide, enteroglucagon, motilin, neurotensin, 5-HT, substance P, pancreatic polypeptide, somatostatin.
substances capable of producing certain biological effects, the most characteristic of which are the changes which occur in mammals at estrus; the naturally occurring estrogenic hormones are β-estradiol, estrone and estriol.
steroids in birds which affect development of the reproductive tubular system, head decorations, feathers, squawk, behavior.
substances sprayed on plants which exert a lethal hormonal effect on the entire plant. See also hormone weedkiller (below).
lactation hormone, lactogenic hormone
luteotropic hormone (LTH)
those stored and released by the neurohypophysis, i.e. oxytocin and vasopressin.
peptide molecules which exert their effects only on target cells that carry the hormone-specific receptors.
one secreted by the placenta, including chorionic gonadotropin, relaxin, and other substances having estrogenic, progestational or adrenocorticoid activity. See also placental hormones.
the presence of hormone-specific receptors on cells is the means of determining which cells respond to the circulating hormones. The number of receptors on each cell is one of the ways of regulating the degree of response.
see sex hormones.
somatotrophic hormone, somatotropic hormone
somatotropin release inhibiting hormone
somatotropin releasing hormone (SRH)
growth hormone releasing hormone.