Submaximal doses of ghrelin do not inhibit gonadotrophin levels but stimulate prolactin secretion in postmenopausal women

Summary

Objective

An inhibitory effect of ghrelin on gonadotrophin secretion has been reported in normally menstruating women possibly modulated by endogenous estrogen. The aim of this study was to examine the effect of ghrelin on gonadotrophin and PRL secretion in estrogen-deprived postmenopausal women.

Design

Prospective intervention study.

Patients and Measurements

Ten healthy postmenopausal volunteer women were studied during two 15-day periods of estrogen treatment (A and B) a month apart. Four experiments (Exp) were performed in total, two on day 1 (Exp 1A and Exp 1B) and two on day 15 (Exp 15A and Exp 15B) of the two periods. The women received in Exp 1A and in Exp 15A two iv injections of ghrelin (0.15 μg/kg at time 0 min and 0.30 μg/kg at time 90 min) and in Exp1B and in Exp 15B normal saline (2 ml) respectively. Blood samples were taken at -15, 0, 30,60, 90, 120, 150 and 180 min.

Results

After estrogen treatment, late follicular phase serum estradiol levels were attained on day 15 of periods A and B. Ghrelin administration did not affect serum levels of FSH and LH, whereas it increased significantly those of GH and PRL. In Exp 15A, serum PRL increment in response to ghrelin (area under the curve, net increment) was significantly greater than in Exp 1A (P<0.05).

Conclusions

The present study demonstrates for the first time that in estrogen-deprived postmenopausal women, ghrelin administration affects neither FSH nor LH levels but stimulates PRL secretion, that is amplified by exogenous estrogen administration.

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