Tropic hormones are hormones that have other endocrine glands as their target. Most tropic hormones are produced and secreted by the anterior pituitary. 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.
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. 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.
- Adrenocorticotropic hormone (ACTH or corticotropin) – stimulates the adrenal cortex to release glucocorticoids.
- Luteinizing hormone (LH) – stimulates the release of steroid hormones in gonads—the ovary and testes.
- Follicle-stimulating hormone (FSH) – stimulates the maturation of eggs and production of sperm.
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.
See also
References
- ^ Purves, William K.; David Sadava; Gordon H. Orians; H. Craig Heller (2001). Life: The Science of Biology (6th ed.). Massachusetts: Sinauer Associates. ISBN 0-7167-3873-2.
- ^ Cambell, Neil A.; Jane B. Reece. Biology (6th ed.). Sinauer Associates. ISBN 0-321-27045-2.
- Steinberg, Werner (1952). "Trophic Vs. Tropic". Journal of the American Medical Association. 149: 82. doi:10.1001/jama.1952.02930180084027.