Sex-Dependent Effect of Metformin on Serum Prolactin Levels In Hyperprolactinemic Patients With Type 2 Diabetes: A Pilot Study.

BACKGROUND: Metformin was found to reduce circulating levels of pituitary hormones.

OBJECTIVE: The purpose of this study was to assess whether sex determines the effect of metformin on lactotroph secretory function.

METHODS: The study population included 25 women and 12 men with mildly elevated serum prolactin levels (25-75 ng/mL). Because of concomitant type 2 diabetes, all participants were treated with metformin (3 g daily). Plasma levels of glucose and lipids, HOMA1-IR, serum levels of prolactin, thyrotropin and free thyroid hormones, as well as Jostel's, SPINA-GT and SPINA-GD indices were assessed at baseline and at the end of metformin treatment.

RESULTS: The study completed 24 women and 11 men. At baseline, there were no significant differences in circulating levels of glucose and lipids, insulin sensitivity, hormones, Jostel's, SPINA-GT and SPINA-GD indices between women and men. In both men and women, metformin reduced fasting glucose levels and HOMA1-IR. However, only in women metformin decreased elevated prolactin levels and this effect correlated with an improvement insulin sensitivity, as well as with the impact on SPINA-GT.

CONCLUSIONS: The results of the study suggest that the effect of metformin on serum prolactin levels is sex-dependent.