Inhibitory effect of submaximal doses of ghrelin on gonadotropin secretion in women

The effect of ghrelin on gonadotropin secretion has been equivocal. Recent data have shown an inhibitory effect of repeated injections of ghrelin on nocturnal LH and FSH secretion in women. The aim of this study was to investigate the effect of submaximal doses of ghrelin on the diurnal secretion of gonadotropins. Ten normally cycling women received 2 consecutive dosages of ghrelin (0.15 μg/kg and 0.30 μg/kg) intravenously in the early and late follicular phases of the cycle. Saline was injected in the preceding cycle. Blood samples in relation to ghrelin or saline administration (time 0 and 90 min) were taken at -15, 0, 30, 90, 120, 150, and 180 min. Serum estradiol concentrations were significantly higher in the late than in the early follicular phase. Following ghrelin administration, serum LH and FSH levels decreased significantly, in relation to the saline injection, in the late (p<0.01), although FSH values showed a within the group decrease also in the early follicular phase (p<0.05). The study suggests a differential action of ghrelin on diurnal gonadotropin secretion throughout the follicular phase of the cycle.