Ovulation induction with bromocriptine in normoprolactinemic anovulatory women

Afternoon-evening and nocturnal serum PRL levels and PRL responsiveness to metoclopramide (MCP) were determined in 34 women with normoprolactinemic anovulation (nPRL-Anov) and in the early follicular phase (EFP) in 6 normal women. Subsequently, the nPRL-Anov women were treated with 5 mg bromocriptine (Br) twice daily for 2 months, and its action on ovulation was determined. Those women who did not respond to Br received 50-150 mg clomiphene for 5 days. The nPRL-Anov patients were classified into 3 groups in terms of the efficacy of Br treatment: group I, those who ovulated with Br (n = 13); group II, those who ovulated after receiving Br and clomiphene (n = 7); and group III, those who failed to ovulate after the above treatments (n = 10). Four patients dropped out of the study. Diurnal serum PRL levels were approximately 10 ng/ml in all patients, and no statistical difference was found among the groups. Peak nocturnal serum PRL levels (the highest PRL value during the 0000-0400 h period) were 38.0 +/- 23.9 (+/- SD) ng/ml in group I patients, higher (P less than 0.05) than in groups II and III and normal (EFP) women (20.1 +/- 9.1, 20.7 +/- 7.7, and 16.3 +/- 2.7 ng/ml for the group II and III patients and the EFP women, respectively). MCP induced rapid and marked elevation in serum PRL levels in all subjects. The maximum post-MCP PRL value in the group I patients was 224.2 +/- 89.7 ng/ml, which was significantly higher (P less than 0.002) than the maximum value in the remaining groups (120.5 +/- 25.8, 121.3 +/- 54.2, and 101.9 +/- 28.1 ng/ml, respectively). Ten (76.9%) and 12 (92.3%) group I patients had nocturnal PRL levels above 25 ng/ml and maximum PRL values after MCP above 150 ng/ml, respectively. We conclude that some nPRL-Anov patients have elevated nocturnal serum PRL levels or enhanced PRL responsiveness to MCP, indicative of nocturnal or latent hyperprolactinemia. Br effectively induced ovulation in these patients. A MCP provocation test can predict the outcome of Br treatment in such nPRL-Anov patients.