Metergoline treatment of hyperprolactinemic states

The ergoline derivative metergoline was administered at the daily dose of 12 mg for 1 to 28 months to 41 hyperprolactinemic women (20 with a normal sella turcica according to tomography, 16 with radiologic evidence of pituitary microadenoma, and 5 with macroadenoma). Serum prolactin (PRL) concentration was reduced by treatment to below 50% of pretreatment values in 29 patients, with actual normalization (serum PRL <20 ng/ml) in 20. There was no difference in the PRL suppression between the patients without and with pituitary tumor. Among 35 subjects with amenorrhea or anovulation treated for a least 2 months, 5 became pregnant, 14 had evidence of ovulation (serum progesterone levels above 3 ng/ml in the presumed luteal phase), and 6 had resumption of cyclic menses. Although the clinical improvement in gonadal function was generally associated with PRL suppression by treatment, ovulation occurred in four patients who had no or minimal decrease in PRL levels, and clinical benefit was lacking despite marked PRL lowering in six, four of whom had impaired gonadotropin secretion. The side effects of the treatment were minimal and transient. The present study shows that metergoline is an effective and safe PRL-lowering drug. Although its mechanism of action is not fully understood, it probably acts as a serotonin antagonist to inhibit PRL release. The finding that ovarian function may be restored in some cases in the absence of PRL suppression suggests that metergoline might directly stimulate gonadotropin release in certain circumstances.