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Objective: It has been suggested that exogenous oestradiol augments ghrelin-induced growth hormone (GH) secretion in postmenopausal women. Whether endogenous oestrogens exert a similar effect during the normal menstrual cycle is not known. The aim of this study was to test the hypothesis that physiological changes in ovarian steroids during the normal menstrual cycle modulate GH and prolactin (PRL) response to ghrelin., Design: Healthy women were studied in three phases of the normal menstrual cycle., Patients: Ten healthy normally cycling women., Measurements: A single dose of ghrelin (1 microg/kg) was administered intravenously in the early and late follicular phases and in the mid-luteal phase of the cycle. Saline was injected in the preceding cycle. Blood samples were taken before ghrelin or saline injection (time 0) and also at -15, 15, 30, 45, 60, 75, 90 and 120 min. The GH and PRL responses were assessed., Results: Serum oestradiol and progesterone concentrations showed the variations of a normal menstrual cycle. After ghrelin administration, in the three phases of the cycle, plasma ghrelin and serum GH and PRL levels increased rapidly, peaking at 30 min and declining gradually thereafter (P < 0.001). There were no significant differences in the hormone levels between the three phases at all time points. No changes in GH and PRL levels were seen after saline injection., Conclusions: These results demonstrate that GH and PRL responses to ghrelin do not change across the menstrual cycle. It is suggested that the action of ghrelin on the pituitary somatotrophs is modulated differentially by endogenous and exogenous ovarian steroids.

Background: It has been suggested that ghrelin may affect reproduction in animals by decreasing pituitary LH secretion. The role of ghrelin on LH secretion in women has not been investigated. Our aim was to assess the effect of ghrelin administration on basal and GnRH-induced LH secretion during the menstrual cycle., Methods: Normally cycling women (n = 10) received on Day 3 of three consecutive cycles a single bolus i.v. of either ghrelin (1 microg/kg, cycle 1) or GnRH (100 microg, cycle 2) or GnRH plus ghrelin (cycle 3). In cycle 1, ghrelin was also injected in late follicular and mid-luteal phase of the cycle. Saline was injected in a preceding cycle (cycle 1, control). Blood samples were taken before drugs or saline injection (time 0) as well as at -15, 15, 30, 45, 60, 75, 90 and 120 min., Results: Plasma ghrelin levels increased rapidly, peaking at 15 or 30 min (P < 0.001), then decreased steadily, approaching pre-injection levels at 120 min. Serum FSH, LH, estradiol and progesterone levels remained unchanged. The stimulating effect of GnRH on LH and FSH secretion was unaffected by ghrelin injection. In contrast to saline, ghrelin stimulated a significant increase in growth hormone levels., Conclusions: Under these experimental conditions, our results demonstrate for the first time the inability of a bolus of ghrelin to affect basal and GnRH-induced LH and FSH secretion. It is suggested that ghrelin does not play a major physiological role in gonadotrophin secretion in women.