Nocturnal prolactin levels in infertility.

Since serum prolactin rises during sleep in normal women, nocturnal serum prolactin concentrations were determined every 30 minutes in follicular phase and again in luteal phase in 13 regularly menstruating infertile women with daytime normoprolactinemia, 8 of whom had luteal phase defects. When compared with controls, there was an increased serum prolactin elevation in 7 women. Six of the women with nocturnal hyperprolactinemia took bromocriptine for two menstrual cycles. This treatment eliminated the excessive nocturnal prolactin rise but did not result in consistent improvement in endometrial development. Polytomographic findings compatible with a pituitary microadenoma were seen in 5 of 7 women with nocturnal hyperprolactinemia. Random daytime prolactin levels may be normal in infertile women who have nocturnal hyperprolactinemia associated with x-ray evidence of pituitary microadenoma.