Prolactin suppression by bromocriptine stimulates aromatization of testosterone to estradiol in women

The effect of follicular phase bromocriptine therapy on the ovarian endocrine response to clomiphene citrate and gonadotropins was studied in 35 tubal infertility patients in a randomized placebo-controlled trial. During bromocriptine treatment, the serum prolactin (PRL) concentration significantly decreased, and consequently the serum estradiol (E2) concentration was significantly higher than in the controls on cycle day 9, and the ratio of testosterone (T) to E2 was decreased from cycle day 8 through day 10. The luteal phase progesterone concentration and the length of the luteal phase were not affected by bromocriptine therapy. The number and quality of oocytes harvested and the cleavage rates were similar in both groups. The present results, together with our previous observations, demonstrate that PRL participates in the regulation of ovarian steroidogenesis, particularly aromatization of T to E2.