Context: The prevalence of non-alcoholic fatty liver disease (NAFLD) in polycystic ovarian syndrome (PCOS) is high. Small studies have shown reductions in serum alanine aminotransaminase (ALT) and gamma-glutamyltransaminase (GGT) concentrations, both surrogate liver fat markers, and sometimes improvements in liver histology in individuals with NAFLD treated with metformin.

Aims: We investigated whether metformin reduces serum ALT and GGT concentrations in obese women with PCOS.

Methods: We performed post hoc data analysis from a trial, involving 82 obese women aged 22-46 years with PCOS, conducted at an academic institution. Participants were treated with metformin 1500 or 2550 mg/day for 8 months. Anthropometric measurements and blood samples (serum ALT, GGT, lipids, leptin, C-reactive protein, insulin, glucose analyses) were taken at baseline, 4 and 8 months.

Results: Sixty-six participants completed the study. Mean weight, serum ALT and GGT decreased from 100.3 to 96.6 kg (p < 0.0001), 29.7 to 25.8 U/l (p = 0.012) and 21.4 to 16.9 U/l (p < 0.0001) respectively. Associations between weight reduction and decreases in serum ALT and GGT were highly significant and independent of change in Homeostasis Model Assessment of Insulin Resistance. In women with baseline ALT > 29.7 U/l (median), ALT reduction was highly significant (p = 0.005); however in those with baseline ALT < 29.7 U/l, ALT did not change despite similar weight reduction. There was no difference in reductions in ALT and GGT when the two metformin doses were compared. Intention-to-treat analyses gave comparable results.

Conclusions: Metformin therapy is associated with reductions in surrogate liver fat markers in obese women with PCOS. This adds indirect support for a benefit of metformin in attenuating/reversing liver fat accumulation in PCOS and more generally.