Body mass index and thyroid function in adolescent girls

Area of Science:

• Endocrinology
• Pediatric Health
• Human Physiology

Background:

• Thyroid hormones play a crucial role in regulating metabolism and energy balance.
• Body Mass Index (BMI) is a common indicator of weight status, with obesity being a growing concern in adolescents.
• Understanding the interplay between thyroid function and BMI is essential for assessing adolescent health.

Purpose of the Study:

• To investigate the relationship between thyroid function markers and BMI in adolescent girls.
• To determine if thyroid hormone levels differ between normal weight and overweight/obese adolescent girls.

Main Methods:

• A cross-sectional study involving 227 adolescent girls (aged 12-21) in Lar province, Iran.
• Serum samples were analyzed for thyroid hormones: Triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH), reverse triiodothyronine (rT3), free thyroxine (FT4), and free triiodothyronine (FT3).
• Weight and height were measured to calculate BMI; subgroup analysis was performed based on BMI categories.

Main Results:

• Thyroid stimulating hormone (TSH), thyroxine (T4), and reverse triiodothyronine (rT3) showed a positive correlation with BMI.
• Adolescent girls with BMI ≥ 25 kg/m² exhibited significantly higher serum TSH, T4, and rT3 levels compared to those with BMI < 25 kg/m².
• Despite normal overall thyroid function, TSH and rT3 levels were positively associated with BMI in the study population.

Conclusions:

• Elevated TSH and rT3 levels are positively correlated with BMI in adolescent girls, even with normal thyroid function.
• TSH and rT3 may serve as potential biomarkers for altered energy balance in overweight and obese adolescent girls.
• Further research is warranted to elucidate the causal mechanisms and clinical implications of these findings.