Purpose: To determine the effect of body composition on thyroid hormones in euthyroid post-pubertal females.
Methods: Thirty post-pubertal females were classified according to the body mass index (BMI) into three equal groups; Group (A) had normal weight (BMI was 18-25 kg/m2), Group (B) were overweight (BMI was 25-30 kg/m2) and Group (C) had grade I obesity (BMI was 30-35 kg/m2). Body composition parameters (BMI, and muscle, water, bone and fat contents) as well as fasting blood levels of thyroid hormones (serum free triiodothyronine (T3), serum free thyroxine (T4) and serum thyroid stimulating hormone (TSH)) were assessed for each female in the three groups.
Results: There were non-significant differences between the three groups (p < 0.05) regarding muscle content, bone content, serum free T3 and serum TSH. However, group (C) had significantly lower water content as well as significantly higher fat content and serum free T4 than group (A) (p < 0.05).
Conclusion: Obesity is associated with low water content as well as high fat content and serum free T4 levels in euthyroid post-pubertal females.