Tropic hormone

Tropic hormones are hormones that have other endocrine glands as their target. Most tropic hormones are produced and secreted by the anterior pituitary.^[1] The hypothalamus secretes tropic hormones that target the anterior pituitary, and the thyroid gland secretes thyroxine, which targets the hypothalamus and therefore can be considered a tropic hormone.^[2]

The term tropic is from Ancient Greek τροπικός (tropikós), in the sense "of or pertaining to a turn or change", meaning "causing a change, affecting"; this is the same origin as tropic and trope. This should not be confused with trophic, as in similar-sounding trophic hormone – the words and concepts are both unrelated.^[3] Tropic hormones are contrasted with non-tropic hormones, which directly stimulate target cells.

Examples

Anterior pituitary

Tropic hormones from the anterior pituitary include:

• Thyroid-stimulating hormone (TSH or thyrotropin) – stimulates the thyroid gland to make and release thyroid hormone.^[4]
• Adrenocorticotropic hormone (ACTH or corticotropin) – stimulates the adrenal cortex to release glucocorticoids.^[5]
• Luteinizing hormone (LH) – stimulates the release of steroid hormones in gonads—the ovary and testes.^[6]
• Follicle-stimulating hormone (FSH) – stimulates the maturation of eggs and production of sperm.^[7][8]

Hypothalamus

In turn, the hypothalamus controls the release of hormones from the anterior pituitary by secreting a class of hypothalamic neurohormones called releasing and release-inhibiting hormones—which are released to the hypothalamo-hypophyseal portal system and act on the anterior pituitary.^[9]

See also

• Endocrine system
• Non-tropic hormone
• Trophic hormone

References