The association between thyroid homeostasis parameters and obesity in subjects with euthyroidism

The relationship between thyroid homeostasis parameters and obesity remains poorly understood in subjects with euthyroidism. This retrospective study aimed to investigate the association between the thyroid homeostasis and obesity in a population with euthyroidism. A total of 201 adult participants with euthyroidism (age range: 27-85 years) were enrolled. Clinical measurements, including obesity indices and biochemical analyses, were conducted. Thyroid homeostasis parameters were calculated. Multiple linear regression analysis was used to analyze the associations between thyroid function, thyroid homeostasis parameters, and obesity measurements. There was a positive correlation between thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), Jostel's thyrotropin index (TSHI), standard TSH index (sTSHI), thyrotroph thyroid hormone sensitivity index (TTSI), sum activity of peripheral deiodinase (SPINA-GD), and body mass index (BMI) in participants with euthyroidism and a negative correlation between thyroid's secretory capacity (SPINA-GT) and BMI (all P<0.05). Only the fT3, TSHI, and sTSHI had a positive correlation with waist circumference (all P<0.05). We concluded that BMI was positively associated with pituitary thyrotropic function parameters and SPINA-GD, and negatively correlated with SPINA-GT in adults with euthyroidism.