Suppression of prolactin secretion during ovarian hyperstimulation is followed by elevated serum levels of endometrial protein PP14 in the late luteal phase.

A double-blind placebo-controlled study on bromocriptine administration during days 2-12 of ovarian hyperstimulation for in-vitro fertilization (IVF) showed that, in bromocriptine cycles, levels of the endometrial protein PP14 were higher in the late luteal phase. This was verified both by calculating forward from the day of human chorionic gonadotrophin (HCG) administration and backward from the onset of the next period. Bromocriptine had no effect on IVF performance. During bromocriptine treatment the serum prolactin levels declined and serum oestradiol levels were higher on day 9 of the cycle. There was a positive correlation (r = 0.55; P = 0.012) between the serum oestradiol levels on day 9 and the PP14 levels on days 22-23 of the cycle. No difference was found in the luteal phase progesterone levels between bromocriptine- and placebo-treated cycles. These results suggest that low prolactin and/or high oestradiol levels during the follicular phase have an influence on the subsequent secretory capacity of the endometrium as reflected by secretion of a specific endometrial protein.