Return of gonadotropic function in postpartum women during bromocriptine treatment.

The rapid postpartum return of gonadotropic function during bromocriptine treatment was investigated through hormonal measurements in 15 women. Luteinizing hormone (LH) was measured by a novel and specific assay that does not cross-react with human chorionic gonadotropin (hCG). Prolactin was effectively suppressed by bromocriptine and hCG was cleared within 2 weeks. During the first week, both follicle-stimulating hormone (FSH) and LH were undetectable. The return of FSH and LH secretion occurred in the second postpartum week and initially was characterized by a high FSH/LH ratio. The causes of the 1-week delay in resumption of pituitary gonadotropin secretion are not known, but endogenous opioids may play a role. The possible relation between the high FSH/LH ratio and low LH pulse frequency also is discussed.