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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, 0.56; P=.35).

CONCLUSIONS

Metformin induces a reduction in TSH levels both in overt and in subclinical hypothyroidism. In contrast, no change in TSH levels is found in euthyroid patients.

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  • Authors+Show Affiliations

    ,

    Department of Clinical Medicine and Surgery, Federico II University, 80131 Naples Italy.

    , , , ,

    Source

    MeSH

    Hormone Replacement Therapy
    Humans
    Hypoglycemic Agents
    Hypothyroidism
    Metformin
    Thyrotropin
    Thyroxine

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Review

    Language

    eng

    PubMed ID

    24203069