Effects of Treatment With Metformin on TSH Levels: A Meta-analysis of Literature Studies
Abstract
CONTEXT: Some data suggest that metformin affects the thyroid profile in patients with type 2 diabetes, but contrasting results are reported in different settings. OBJECTIVE: The aim of this meta-analysis was to assess the effect of metformin treatment on TSH in subjects with or without thyroid dysfunction. DATA SOURCES: We performed a systematic search of articles evaluating changes in TSH levels in patients receiving metformin. STUDY SELECTION: Studies evaluating TSH levels before and after metformin treatment were included. DATA EXTRACTION: Clinical data, demographic variables, and TSH levels before and after treatment with metformin were extracted. Data were analyzed according to the underlying thyroid disease. DATA SYNTHESIS: A total of 7 datasets (206 patients) were included in the final analysis. After metformin treatment, a slight but significant reduction in TSH levels was found in 4 datasets on 119 patients with overt hypothyroidism receiving l-T4 replacement (mean difference, 1.08; 95% confidence interval [CI], 0.50, 1.65; P=.0003). Similarly, in 2 datasets reporting on a total of 33 patients with subclinical hypothyroidism not receiving treatment with l-T4, a significant reduction in TSH levels was reported (mean difference, 1.59; 95% CI, 1.32, 1.87; P<.00001) after treatment with metformin. In 1 dataset, including 54 euthyroid patients not receiving l-T4, no changes in TSH levels were reported after treatment with metformin (mean difference, 0.18; 95% CI, -0.20,…
How strong is the evidence?
Evidence Hub reads this as a meta-analysis. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid. Reported size: 206 participants or records.
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