Free triiodothyronine and free thyroxine hormone levels in relation to breast cancer risk: a meta-analysis.

Introduction: The conflict between breast cancer (BC) and thyroid hormone (TH) has been studied for years. The purpose of the study was to summarise and analyse the available data on the relationship between TH and BC.

Material And Methods: The PubMed, EMBASE, Cochrane Library, and Google Scholar databases were searched to identify relevant studies. The mean difference (MD) with 95% confidence interval (CI) were calculated by fixed or random effects models to assess the effect sizes.

Results: Thirteen eligible studies with 5957 participants were included in the meta-analysis. The result of this study indicates that there is a significant risk relationship between BC and thyroid hormones [free triiodothyronine (FT3): MD = 1.01 pmol/L, 95% CI: 0.32-1.70, free thyroxine (FT4): MD = 0.26 ng/dL, 95% CI: 0.13-0.38].

Conclusions: Compared with healthy controls, the positive risk of FT3 and FT4 is higher in BC.