New Anthropometric Measurements: Relationship to Thyroid Functions in Euthyroid Obese Subjects

Introduction Body mass index (BMI) is unable to make a distinction between muscle mass and fat mass. Therefore, new anthropometric measurements, such as a body shape index (ABSI), body round index (BRI), and body adiposity index (BAI), have been formulated in recent years. Many studies have reported a correlation between BMI and thyroid function. In this study, we aimed to investigate the relationship between the above-mentioned new anthropometric measurements and thyroid functions in euthyroid obese subjects. Methods We included 675 euthyroid (TSH ≥ 0.4 and < 4.5 mIU/l) individuals from the obesity outpatient clinic, aged between 18 and 65 years old, with BMI ≥ 30. Thyroid-stimulating hormone (TSH), free T4 (fT4) and free T3 (fT3), anthropometric measurements (weight, height, and waist circumference), and bioelectric impedance analyses [percent body fat (PBF) and fat-free mass (FFM)] of individuals were measured and recorded. ABSI, BRI, and BAI were calculated with the data from these measurements. Anthropometric measurements were compared to thyroid function tests. Results Eighty percent of the subjects were female. The mean age and BMI were 38 ± 17 years and 38 ± 6 kg/m(2), respectively. TSH was found to be negatively correlated with ABSI (p = 0.006) and positively correlated with BAI (p < 0.001), but a statistically significant relationship with BRI (p = 0.193) was not determined. Free T4 was not associated with any of the anthropometric measurements.While fT3 was determined to be positively correlated with ABSI (p = 0.008) and negatively correlated with PBF and BAI (p = 0.001, p = 0.002, respectively), no statistically significant relationship with fT3 and BRI was determined. Conclusion TSH is positively correlated with measurements of adiposity such as BMI, PBF, BAI while indexes in which abdominal obesity increases, such as waist circumference (WC), waist-hip ratio (WHR), and ABSI, are correlated with fT3 levels.