GHRH
Summary
Growth Hormone-Releasing Hormone (GHRH) is a hypothalamic peptide hormone that stimulates growth hormone (GH) release from anterior pituitary somatotrophs. It acts via cAMP pathway and is essential for normal growth and development. GHRH deficiency causes growth hormone deficiency, while GHRH-secreting tumors can cause acromegaly.
Detail
GHRH is a 44-amino acid peptide synthesized in the arcuate nucleus of the hypothalamus and released into the hypothalamic-hypophyseal portal circulation. It binds to GHRH receptors on somatotrophs in the anterior pituitary, activating adenylyl cyclase and increasing cAMP levels, which stimulates GH synthesis and release. GHRH release is pulsatile and influenced by sleep (increased during slow-wave sleep), exercise, stress, hypoglycemia, and amino acids. It is inhibited by somatostatin (GHIH) from the hypothalamus and IGF-1 negative feedback. Pathologically, GHRH deficiency can result from hypothalamic lesions, causing isolated GH deficiency and short stature in children. Ectopic GHRH secretion from pancreatic islet cell tumors, carcinoid tumors, or other neuroendocrine tumors can cause acromegaly by stimulating excessive GH release. GHRH analogs are used therapeutically to diagnose GH deficiency and assess pituitary reserve.
Sources
- First Aid for the USMLE Step 1
- Robbins Basic Pathology
- Harrison's Principles of Internal Medicine
- Costanzo Physiology
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