Author(s): Shailendra D1, Mrinal D2, Subbaratnam Y3, Prasuna G4
BACKGROUND AND RATIONALE: Metformin use is reported to be associated with reduction in serum thyroid stimulating hormone (TSH) levels. However, recent reports suggest that the effect of metformin on TSH is seen only in those who have hypothyroidism and not in those who are euthyroid.
OBJECTIVES: The objective of this study was to compare the difference in TSH levels between euthyroid type 2 diabetes mellitus (T2DM) patients on metformin versus those not on metformin.
RESEARCH DESIGN AND METHODS: Using a cross sectional study design subjects with type 2 diabetes mellitus (N=150) were recruited from a rural community using simple random sampling. Individuals with known thyroid dysfunction were excluded. Data on socio-demographic variables, medications being used and duration of use were collected using structured questionnaire. Laboratory measurements included thyroid function tests, complete blood count, hepatic function tests, renal function tests and HbA1c estimation.
RESULTS: The median TSH levels in patients with T2DM on metformin was 1.98 mIU/L (Q1=1.24mIU/L, Q3=2.76 mIU/L), whereas in patients with T2DM not on metformin the median TSH levels was 2.12mIU/L (Q1=1.30mIU/L, Q3=2.87mIU/L.)There was no statistically significant difference in the median TSH levels between patients with type 2 diabetes mellitus on metformin and those not on metformin (p=0.23).Further, there was no correlation between metformin dose and serum TSH levels (p=0.36).
CONCLUSIONS: Metformin use did not affect serum TSH levels in euthyroid patients with T2DM.