Predictors of Serum TSH in a Healthy Adult Sample of the Lebanese Population

Purpose: Measuring thyroid-stimulating hormone (TSH) is essential for diagnosing and monitoring thyroid diseases. The aim of this study is to determine the factors predicting TSH variability. Materials and Methods: Plasma TSH, free T3 (FT3), total T3 (TT3), free T4 (FT4), anti-peroxidase antibodies (TPOAb) and anti-thyroglobulin antibodies (TgAb) were measured in 301 healthy Lebanese adults (198 women and 103 men) aged 18 to 65 years. Measurements were performed on the Cobas Roche automate. Age, sex, Body Mass Index (BMI), arterial blood pressure and the presence of dyslipidemia were collected from the population. Results: The mean age of the population was 38.98 ± 13.28 years and the mean BMI 25.36 ± kg/m². There was no correlation between TSH and FT4, while a positive correlation was found between TSH and TT3, FT3, TPOAb and TgAb (respectively p <0.001, p=0.002, p<0.0001and p< 0.0001). TSH was not associated with age or gender but was positively correlated with BMI (p=0.053) and systolic blood pressure (p=0.03).In a multiple linear regression analysis, the independent predictors of TSH were FT4, FT3 and TPOAb. In addition, FT4, TPOAb, and dyslipidemia were independently associated with the TSH 97.5th percentile. Conclusion: Our study showed that the main predictors of TSH are FT4, FT3 and TPOAb. This finding supports the role of TSH in enhancing T3 production as well as the main role of TPOAb in predicting the rise in TSH.