Growth hormone releasing hormone

Growth-hormone-releasing hormone (GHRH), also known as growth-hormone-releasing factor (GRF or GHRF) or somatocrinin, is a 44-amino acid peptide hormone produced in the arcuate nucleus of the hypothalamus.

GHRH is released from neurosecretory nerve terminals of these arcuate neurons, and is carried by the hypothalamo-hypophyseal portal circulation to the anterior pituitary gland where it stimulates growth hormone (GH) secretion. GHRH is released in a pulsatile manner, stimulating similar pulsatile release of GH. In addition, GHRH also promotes slow-wave sleep directly.

Relationship of GRH & somatostatin

The actions of GHRH are opposed by "growth-hormone-inhibiting hormone", more commonly termed somatostatin.

Somatostatin is released from neurosecretory nerve terminals of periventricular somatostatin neurons, and is carried by the hypothalamo-hypophysial portal circulation to the anterior pituitary where it inhibits GH secretion. Somatostatin and GHRH are secreted in alternation, giving rise to the markedly pulsatile secretion of GH.

Sequence

The amino acid sequence of GHRH is:

Tyr - Ala - Asp - Ala - Ile - Phe - Thr - Asn - Ser - Tyr - Arg - Lys - Val - Leu - Gly - Glu - Leu - Ser - Ala - Arg - Lys - Leu - Leu - Gln - Asp - Ile - Met - Ser - Arg - Glu - Gln - Gly - Glu - Ser - Asn - Gln - Glu - Arg - Gly - Ala - Arg - Ala - Arg - LeuNH2

References