A META-ANALYSIS FOR ANALYZING CHANGES IN SERUM-FREE T4 LEVELS WITH METFORMIN TREATMENT INPATIENTS WITH OR WITHOUT THYROID DISEASE AND/OR DIABETES

Context: Previous studies suggestthe effect of metformin on TSH levels, but its impacton free T4 (fT4) levels has not been understood clearly.

Objective:This Meta-analysis aims to studythe effects of metformin on serum-free T4(fT4) levels in patients with or without underlying thyroid disease and/or diabetes.

Data Sources:We reviewed articles from the Cochrane Library based on the systematic protocol.

Data Extraction: Demographic, clinical, and relevant data was extracted. Data were analyzed according to the changes in fT4 levels with metformin administration.

Data Synthesis: A total of 5 datasets (475 patients) were included in our analysis. There was a reduction in free thyroxine levels evident bythe statistically significant mean difference in this meta-analysisin the treatment group between the baseline levels and post-follow-up (Metformin MD= 1.0 pg/ml, CI=0.3423 to 1.657, P value=0.005).

Conclusion:While this meta-analysis found no significant overall effect of metformin on fT4 levels in patients with or without underlying diabetes or thyroid disease, the results from individual studies like Oleandri et al. (1999) suggest that metformin may cause a slight decrease in fT4 levels. However, given the small effect size and minimal clinical significance, the impact of metformin on fT4 levels remains uncertain and warrants further investigation to better understand its clinical relevance. Clinically, anthropometric and metabolic characteristics can alter these levels differently in each case. Dose adjustment for Levothyroxine (LT4) replacement in patients is the main concern when metformin is given concomitantly.