Ghrelin strongly stimulates growth hormone (GH) release in humans

Ghrelin is a recently identified endogenous ligand for the GH secretagogue receptor and is involved in a novel system for regulating GH release. Howev er, little is known about its GH-releasing activity and other endocrine eff ects in humans. To address this issue, we studied the GH, ACTH, cortisol, P RL, LH, FSH, and TSH responses to synthetic human ghrelin. In four normal m ale adults (28-37 yr), iv ghrelin administration released GH in a dose-depe ndent manner and 0.2, 1.0, and 5.0 mug/kg ghrelin produced 43.3 +/- 6.0, 81 .5 +/- 12.7, and 107.0 +/- 10.7 ng/mL of the GH peak values at 30 min, resp ectively. ACTH, cortisol, and PRL levels were also elevated after ghrelin i njection, while the lowest dose (0.2 mug/kg) resulted in only minimum peak values of these hormones (22.8 +/- 3.0 pg/mL, 9.4 +/- 1.9 mug/dL, and 4.6 /- 0.6 ng/mL, respectively). There were no significant changes in LH, FSH, or TSH levels. This is the first study showing evidence that ghrelin strong ly stimulates GH release in humans.