Abstract
Background: Metformin decreases serum levels of monomeric prolactin. No previous study has investigated
the effect of metformin on macroprolactin content in patients with macroprolactinemia.
Methods: We studied three age-, sex- and weight-matched groups of patients: 15 women with
monomeric prolactin, 12 women with macroprolactin, as well as 15 women with normal
prolactin levels. Because of coexisting 2 diabetes or prediabetes all patients were
treated with metformin (1.7–3 g daily). Plasma lipids, glucose homeostasis markers,
as well as serum levels of prolactin and macroprolactin were assessed at baseline
and after 4 months of metformin treatment.
Results: As expected, metformin reduced plasma glucose and triglycerides, as well as improved
insulin sensitivity in all treatment groups. Moreover, the drug reduced post-polyethylene
glycol prolactin levels and tended to reduce pre-polyethylene glycol prolactin levels
in women with monomeric prolactin but not in women with macroprolactinemia and women
with normal prolactin levels.
Conclusion: The obtained results indicate that metformin has a negligible effect on macroprolactin
levels.
Key words
hyperprolactinemia - macroprolactin - monomeric prolactin - insulin resistance