Background:
Metformin as well as
dopaminergic agents exert a beneficial effect on
glucose and lipid metabolism, often impaired in patients with
hyperprolactinemia. Objective: The aim of this study was to compare metabolic- and
prolactin-lowering effects of low-dose
bromocriptine/
metformin combination
therapy and
cabergoline in patients with elevated
prolactin levels. Methods: The study included 27 women with
hyperprolactinemia and
impaired glucose tolerance who were treated with moderate doses of
bromocriptine but experienced adverse effects of this treatment. In 12 of these patients
bromocriptine was replaced with
cabergoline (group A), while the remaining ones continued treatment with
bromocriptine, the dose of which was halved, and administered together with
metformin (group B). Plasma
lipids,
glucose homeostasis markers, as well as serum levels of
prolactin,
thyrotropin and
insulin-like growth factor-1 (IGF-1) were assessed before and after 4 months of
metformin treatment. Results: Both groups did not differ in baseline levels of plasma
glucose and
lipids, in
insulin sensitivity, as well as in circulating levels of all measured
hormones. All patients from group A and 12 patients from group B completed the study.
Cabergoline reduced
prolactin levels, while no effect on plasma
prolactin was found in group B. Neither
cabergoline nor
bromocriptine plus
metformin affected circulating levels of
thyrotropin and
IGF-1. Both treatment options, particularly low-dose
bromocriptine plus
metformin, improved
glucose and
lipid homeostasis. Conclusions: Low-dose
bromocriptine combined with
metformin may be an interesting alternative to
cabergoline in patients with mild
hyperprolactinemia and early
glucose metabolism abnormalities, in whom moderate doses of
bromocriptine are poorly tolerated.