Effects of nocturnal hyperprolactinemia on ovarian luteal function and galactorrhea.

To determine the effects of nocturnal hyperprolactinemia on luteal function and galactorrhea we studied six diurnal normoprolactinemic women with regular menstrual cycles. The diurnal serum levels of prolactin (PRL), luteinizing hormone (LH) and progesterone (Prog) and the nocturnal PRL levels at 1 h intervals were determined throughout the first menstrual cycle. Four of the women were nocturnally normoprolactinemic and two showed nocturnal hyperprolactinemia and low luteal progesterone values. In the second menstrual cycle, they were given metoclopramide (10 mg) at midnight before sleep every day, and their serum levels of PRL, LH and Prog were determined by the same protocol as in the first cycle. During treatment with metoclopramide, all the women showed nocturnal hyperprolactinemia, but their diurnal PRL levels remained within the normal range. Low luteal Prog values were observed in all of them and the peak LH levels decreased in all four nocturnally normoprolactinemic women. They had galactorrhea but neither of the nocturnally hyperprolactinemic women had galactorrhea. These results suggest that nocturnal hyperprolactinemia is a cause of luteal insufficiency and galactorrhea.