Correlation between estradiol-to-testosterone ratio and thyroid peroxidase antibody positivity in men with treatment-naïve primary hypothyroidism or euthyroidism.

Objective: Thyroid diseases pose a substantial socioeconomic burden globally. The aim of this study was to evaluate the correlation between estradiol-to-testosterone (E2/T) ratio and thyroid peroxidase antibody (TPOAb) positivity in male patients with hypothyroidism or euthyroidism. Subjects and methods: Cross-sectional observational study including 115 male patients with hypothyroidism or euthyroidism. The patients were divided into two groups based on positive or negative TPOAb results, with TPOAb positivity defined by a serum TPOAb value ≥ 35 IU/mL. Results: Patients with positive TPOAbs, compared with those with negative TPOAbs, had a higher prevalence of goiter and obesity and higher levels of total cholesterol, triglycerides, and low-density lipoprotein (LDL) cholesterol. The median estradiol level was higher, and the median total testosterone and sex-hormone binding globulin (SHBG) levels were lower in the TPOAb-positive versus the TPOAb-negative group (p < 0.001). In subgroup analysis including only patients with hypothyroidism (n = 80), the median E2/T ratio was higher in the TPOAb-positive group (p = 0.016). The prevalence of TPOAb positivity increased with the increase in E2/T ratio quartiles, from 37.9% in the lowest quartile to 96.2% in the highest quartile (p value for trend across all quartiles < 0.001). On adjusted multivariate analysis, the E2/T ratio emerged as an independent predictor of TPOAb positivity. An E2/T ratio cutoff value of 6.565 x10-3 demonstrated the best diagnostic accuracy, with a sensitivity of 78.2% and specificity of 67.6%. Conclusion: The present study provides insights into the role of the E2/T ratio as a predictor of thyroid disorders.