Association between thyroid function and obesity phenotypes in healthy euthyroid individuals: an investigation based...

Area of Science:

• Endocrinology
• Metabolic Health
• Thyroid Function

Background:

• Thyroid hormones play a crucial role in regulating metabolism.
• Obesity is associated with various metabolic abnormalities.
• The relationship between thyroid function and obesity phenotypes in euthyroid individuals requires further elucidation.

Purpose of the Study:

• To investigate the association between thyroid function and different obesity phenotypes among euthyroid adults.
• To determine if thyroid hormone levels differ across metabolically healthy and unhealthy normal weight and obese individuals.

Main Methods:

• Cross-sectional analysis of 2988 euthyroid adults from the Tehran Thyroid Study (TTS).
• Classification of participants into four obesity phenotypes: metabolically healthy normal weight (MHNW), metabolically healthy obese (MHO), metabolically unhealthy normal weight (MUNW), and metabolically unhealthy obese (MUO).
• Comparison of thyroid hormone levels (TSH, FT4) among phenotypes using ANCOVA, with adjustments for confounding variables and subgroup analyses by age and sex.

Main Results:

• Euthyroid individuals with MHNW phenotype exhibited higher free thyroxine (FT4) levels compared to metabolically unhealthy obese individuals.
• No significant differences in thyroid-stimulating hormone (TSH) levels were observed across obesity phenotypes.
• Subgroup analysis revealed FT4 differences were significant only in individuals younger than 55 years.

Conclusions:

• Metabolic abnormality in overweight/obese euthyroid individuals is independently associated with lower-normal FT4 levels.
• Further research is warranted to understand the mechanisms linking low FT4 to metabolically unhealthy states in euthyroid populations.
• These findings highlight a potential role for thyroid function in the metabolic consequences of obesity.