Effect of metformin of TSH levels

Abstract

Aims and objectives:  Main aim of the study was to see the effect of metformin on thyroid function parameters especially TSH. We also wanted to see factors responsible for these thyroidal effects of metformin.

Materials and methods:  we selected treatment naïve type 2 diabetes and PCOS subjects. we had 72 subjects, 56 were having type 2 diabetes and 16 were having PCOS. We took their blood samples at baseline before starting metformin and 6 months after starting metformin. In both samples we checked thyroid functions and insulin resistance indices. Dose of metformin was 1 gm in type 2 DM and 500mg PCOS. We took 80 patients at beginning, 8 were lost to follow up, 72 completed the study.

Results:  we found that there was no significant change in thyroid function parameters after 6 months of metformin intake.  It made no difference whether patients were obese or non obese, diabetic or nondiabetic, male or female. But on subgroup analysis it was found that in those patients in whom insulin resistance decreased, TSH was significantly decreased where as in  those subjects in which  insulin resistance had increased  TSH did not change significantly.

Conclusion: In this study we concluded that metformin decreases TSH especially in those patients where it decreases insulin resistance also successfully.

Clinical Significance: Minor elevations in TSH may be part of metabolic syndrome and may not warrant treatment with thyroxine.