Role of transient hyperprolactinemia in the late follicular phase of the gonadotropin-stimulated cycle.

Abstract

Background: Serum prolactin (PRL) concentration is known to transiently increase in rats; however, its change is obscure and the role of it is also unclear in women. We studied the relationship between estradiol (E2) and PRL production and the role of transient hyperprolactinemia in the late follicular phase of the gonadotropin-stimulated cycle. Methods: (1) Serum E2 and PRL concentrations were measured on an early follicular day and immediately before a human chorionic gonadotropin (hCG) injection in 60 patients with normoprolactinemia. Twelve of the 60 patients also received a gonadotropin injection with bromocriptine, and serum hormone levels were compared with those without bromocriptine. (2) Preovulatory serum E2 and PRL concentrations were compared between the natural and clomiphene treatment cycles in 14 hormonally normal women. (3) Changes of serum PRL concentrations were measured before and after E2 loading in five premature ovarian failure (POF) patients. (4) The E2 production by granulosa cells in the presence of PRL was measured. Results and Conclusion: Serum E2 and PRL concentrations were significantly increased by the gonadotropin injection. Bromocriptine treatment completely inhibited the PRL increase, but further increased serum E2 concentration on the late follicular day. The E2 loading increased serum PRL levels in POF patients. The clomiphene treatment increased serum E2 but decreased PRL concentrations. Prolactin significantly decreased E2 production by granulosa cells. A feedback loop may exist between E2 and PRL to control the excess E2 production induced by gonadotropin injection. (Reprod Med Biol 2002; 1: 69-74).