Growth hormone-releasing hormone (GHRH)
Also known as: GHRH, somatocrinin, somatoliberin
A 44-amino-acid peptide from arcuate neurons that stimulates GH synthesis, secretion and somatotroph proliferation, acting in balance with inhibitory somatostatin.
Overview
GHRH is released into the portal circulation in pulses that, together with withdrawal of somatostatin, generate the episodic secretion of GH — the largest pulse occurring soon after the onset of slow-wave sleep. It binds the GHRH receptor, a Gs-coupled GPCR; cAMP stimulates GH release, transcription of the GH gene (via the transcription factor PIT-1 and CREB) and somatotroph proliferation.
GH output reflects the balance of three hypothalamic/gut signals: GHRH (+), somatostatin (−) and ghrelin (+, acting via the GH secretagogue receptor). IGF-1 and GH feed back to inhibit GHRH and stimulate somatostatin.
- Location
Source: arcuate (infundibular) nucleus → median eminence. Target: somatotrophs of the anterior pituitary.
Function
- Stimulates GH release and synthesis.
- Promotes somatotroph proliferation.
- Promotes slow-wave sleep.
- Physiology
Class: 44-amino-acid peptide (GHRH 1–44; residues 1–29 carry full activity). Receptor: GHRH-R (Gs → cAMP).
- Regulation
Stimulated by hypoglycaemia, fasting, exercise, sleep, stress, α2-adrenergic agonists; inhibited by GH and IGF-1 (short- and long-loop feedback) and by somatostatin.
Clinical significance
Ectopic GHRH
Rarely, neuroendocrine tumours (pancreatic or bronchial carcinoids) secrete GHRH, producing acromegaly with somatotroph hyperplasia rather than an adenoma.
GHRH receptor mutations
Loss-of-function mutations cause isolated GH deficiency with proportionate short stature.
Compiled from standard anatomy and physiology references — see the Endocrine System sources. For education only; not medical advice.