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Meta-Analysis
. 2023 Oct 31;13(1):18757.
doi: 10.1038/s41598-023-43266-9.

The effect of metformin therapy on serum thyrotropin and free thyroxine concentrations in patients with type 2 diabetes: a meta-analysis

Alireza Amirabadizadeh  1 , Atieh Amouzegar  1 , Ladan Mehran  1 , Fereidoun Azizi  2
Affiliations
Meta-Analysis

The effect of metformin therapy on serum thyrotropin and free thyroxine concentrations in patients with type 2 diabetes: a meta-analysis

Alireza Amirabadizadeh et al. Sci Rep. .

Abstract

Type 2 diabetes and thyroid function disorders are two common chronic endocrine disorders with the high prevalence in various populations. Metformin is well established as the first-line drug therapy for managing diabetes mellitus. In this meta-analysis, we aimed to determine the effect of metformin on serum TSH and FT4 concentrations in patients with type 2 diabetes. We searched PubMed, Scopus, web of science, Cochrane library, and google scholar to collect information on the effect of metformin on serum TSH and FT4 levels. Demographic and clinical information and serum TSH and FT4 concentrations before and after metformin treatment were extracted. Studies on patients over 18 years of age were included. A total of 11 studies including 1147 patients were selected for the final analysis. In hypothyroid patients, the TSH level decreased significantly after treatment with metformin (Hedges's g:1.55, 95%CI 0.93-2.16, p-value < 0.001); FT4 level increased slightly after taking metformin, but the increase was not significant (Heddges's g: - 0.30, 95%CI - 0.90,0.31, p-value = 0.34). In euthyroid subjects, the slight decrease found in TSH and FT4 concentrations was not statistically significant. Metformin reduces TSH levels in hypothyroid patients; however, it has no effect on TSH levels in euthyroid patients. Metformin does not affect serum FT4 levels in euthyroid and hypothyroid patients.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Flow diagram demonstrating the study selection for meta-analysis. # Three studies were performed on hypothyroid and euthyroid patients.
Figure 2
Figure 2
Risk assessment bias for the meta-analysis.
Figure 3
Figure 3
Forest plot to compare serum TSH levels before and after metformin therapy in euthyroid patients.
Figure 4
Figure 4
Forest plot to compare serum FT4 levels before and after metformin therapy in euthyroid patients.
Figure 5
Figure 5
Forest plot to compare serum TSH levels before and after metformin therapy in hypothyroid patients under LT4 monotherapy.
Figure 6
Figure 6
Forest plot to compare serum FT4 levels before and after metformin therapy in hypothyroid patients under LT4 monotherapy.
See this image and copyright information in PMC

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