Tropic hormones influence the release of hormones from other endocrine glands. They feedback inhibit their own production and the secretion of regulatory hormones that stimulate their release. Releasing hormones are tropic hormones secreted by the hypothalamus that stimulate synthesis and secretion of anterior pituitary hormones.
Hypothalamic regulatory hormones pass through portal blood vessels to travel to the anterior pituitary gland. There, the hypothalamic hormones stimulate release of anterior pituitary hormones, some of which are themselves tropic hormones, such as TSH and ACTH. TSH (thyroid-stimulating hormone) stimulates the thyroid to produce thyroid hormones. ACTH (adrenocorticotropin hormone) stimulates the adrenal cortex to produce cortisol.
Other anterior pituitary hormones act directly on organs in the body, such as FSH, prolactin, and growth hormone. FSH (follicle-stimulating hormone) and LH (luteinizing hormone) act on the gonads. Prolactin stimulates milk production and GH (growth hormone) stimulates systemic growth.
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