Functions of central nervous system neurotransmitters in regulation of growth hormone secretion.

Pituitary growth hormone (GH) secretion is regulated by two hypothalamic factors: somatostatin, a characterized tetradecapeptide, which inhibits secretion, and GH-releasing factor, unidentified, which stimulates secretion. Biogenic amines, including norepinephrine, dopamine, serotonin, acetylcholine, and gamma-aminobutyric acid have excitatory or inhibitory effects at brain sites to modulate hypothalamic control. alpha-Adrenergic mechanisms have been shown to be of particular importance in the regulation of physiologic GH secretion, which is characterized by episodic surges of release.