Context: Ghrelin affects the hypothalamic-pituitary-gonadal axis in various nonhuman mammalians, predominantly by suppressing secretion of LH. However, for humans, no such evidence exists.
Objective: Our objective was to study the effect of ghrelin on secretion of LH and testosterone in humans.
Design, participants, and intervention: Nocturnal (2000-0700 h) secretion profiles of LH and testosterone were determined in 10 healthy males (25.7 +/- 3.0 yr) twice, receiving 50 microg ghrelin or placebo at 2200, 2300, 2400, and 0100 h, in this single-blind, randomized, cross-over study.
Results: Ghrelin was associated with significantly (P < 0.05) lower mean plasma levels of both LH (2340-0200 h) and testosterone (0040-0300 h) than placebo. LH peak levels of the pulse after first administration of ghrelin/placebo were significantly (P = 0.014) smaller in the ghrelin (2.98 +/- 1.34 mIU/ml) than in the placebo condition (4.37 +/- 1.09 mIU/ml). In addition, the interval between this and the preceding peak was significantly (P = 0.010) longer in the ghrelin (255.8 +/- 79.1 min) than in the placebo condition (190.8 +/- 51.0 min). Significantly (P = 0.005) more LH pulses occurred with placebo (3.2 +/- 0.75) than ghrelin (2.6 +/- 0.7) subsequent to ghrelin/placebo administration.
Conclusions: Ghrelin caused both a delay and suppression of the amplitude of LH pulses. These findings are in accordance with those in nonhuman mammalians.