Effect of metformin therapy on thyroid-stimulating hormone levels in women with polycystic ovarian syndrome

Abstract

Introduction: Metformin has been shown to decrease thyroid-stimulating hormone (TSH) levels without effect on total T4 and total T3 levels, especially in patients with underlying thyroid dysfunction. The Aim of the Study: To evaluate the effect of metformin therapy on TSH levels in polycystic ovarian syndrome (PCOS) patients who were euthyroid with or without treatment. Design of the Study Nonrandomized prospective intervention trial. Materials and Methods: The study included all euthyroid PCOS patients of the reproductive age group diagnosed according to the modified Rotterdam criteria and the patients were divided into two groups. The first group was put on lifestyle modification alone (Group-I), whereas the second group was put on lifestyle modification and metformin therapy (Group-II). In both groups of patients, TSH, total T4, and total T3 levels were done at baseline and after 3 months of follow-up. Results: A total of 105 patients with PCOS were nonrandomly assigned to Group I (n = 53) and Group II (n = 52). The baseline parameters (age, body mass index, TSH, and Homeostatic Model Assessment for Insulin Resistance) were similar. Thirty-six patients in Group I and 39 in Group II were followed up for 3 months. The change in TSH levels in both groups was not significant at follow-up (Group I [2.56 ± 0.87 vs. 3.01 ± 1.54; P = 0.102] and Group II [2.90 ± 0.81 vs. 2.76 ± 1.26;P = 0.503]). In a subgroup analysis in patients who had thyroid dysfunction, there was a significant decrease in TSH levels in Group II (3.10 ± 0.54 vs. 2.57 ± 0.50;P = 0.031). Conclusion: Metformin significantly decreased TSH levels in women with PCOS with underlying thyroid dysfunction, while it did not show any effect on women without underlying thyroid dysfunction.