Metformin decreases bone turnover markers in polycystic ovary syndrome:a post hoc study

Objective: To study the effects of metformin treatment on bone turnover in women with polycystic ovary syndrome (PCOS), as measured by serum concentrations of bone turnover markers. Design: Post hoc study of a previously conducted prospective multicenter, placebo-controlled, randomized study. Setting: University clinic. Patient(s): The study cohort consisted of 74 non-obese women (body mass index < 27 kg/m²) and 44 obese women (body mass index ≥ 27 kg/m²) diagnosed with PCOS, with a mean age of 27.6 ± 4.0 (SD) years. Intervention(s): Randomization to receive metformin or placebo for 3 months. Main Outcome Measure(s): Serum levels of bone formation marker procollagen type I amino-terminal propeptide (PINP) and bone resorption marker carboxy-terminal cross-linking telopeptide of type I collagen (CTX) at baseline and after metformin/placebo treatment. Result(s): Serum levels of PINP and CTX were similar between the metformin and placebo groups at baseline in the whole study population. Obese women, when compared with non-obese, had lower baseline levels of PINP and CTX. Levels of PINP and CTX were significantly reduced in the whole study population, as well as in both non-obese and obese women after 3 months of metformin treatment, whereas no significant changes were observed in the placebo group. Conclusion(s): Metformin treatment, when compared with placebo, was associated with reduced bone turnover, as suggested by reductions in markers of bone formation and resorption, leading to slower bone remodeling in premenopausal women with PCOS.