Evaluation of thyroid hormone dysfunction in type - 2 diabetes patients on metformin therapy ? A cross sectional study

Diabetes and thyroid diseases are two familiar endocrinopathies seen in the general population. Abnormal thyroid hormone levels can also be found in individuals with diabetes. Metformin may lower thyroid stimulating hormone levels both in hypothyroid as well as euthyroid individuals. To this purpose, we studied analysis of serum TSH levels in patients with type-2 DM who were receiving metformin and compared them with serum TSH levels of those individuals with T2DM that were not on metformin. Study participants were selected from the people residing in neighbouring villages in and adjoining Kadapa district of Andhra Pradesh. Study duration was 6 months between June-November 2008. Sample size was 80 subjects with T2DM on Metformin and 80 subjects with T2DM receiving non Metformin based therapy were included in the study. Data were entered in Microsoft Excel 2007 and data was expressed as mean and standard deviation (Mean±SD). Serum TSH values, metformin dose and metformin duration were not normally distributed. Comparison of difference in means between the two groups for normally distributed continuous variables namely, age, HbA1c, serum T3 and T4 was done by unpaired student’s t test. P <0.05 was treated as significant. Metformin utilize was not associated with changes in serum thyroid stimulating hormone levels in euthyroid type-2 DM patients. The presence of a comparative group of type 2 diabetes individuals not receiving Metformin add to the analytical value of the study design.