Thyroid Disorder in Obese Children and Adolescents: A Cross-Sectional Study in a Tertiary Care Hospital in Bangladesh

Background: Childhood obesity is becoming an increasingly pressing issue on a global scale. This study aimed to explore the relationship between thyroid hormone levels and body mass index (BMI) in obese children and adolescents, an area with limited research, particularly in Bangladesh. Methods: This cross-sectional study was undertaken in Bangabandhu Sheikh Mujib Medical University, Bangladesh, from August 2018 to January 2020. We included 105 participants aged 10–18 years, divided into obese (n = 69) and normal-weight (n = 36) groups based on the CDC BMI percentiles. We conducted chi-square tests, Pearson correlation, and linear regression analyses. Results: Obese participants exhibited significantly higher mean levels of TSH (4.40 ± 3.20 µIU/mL vs. 2.26 ± 0.97 µIU/mL, p-value 0.0002) and FT3 (3.52 ± 0.71 pg/mL vs. 3.02 ± 0.48 pg/mL, p-value < 0.001) and lower FT4 levels (1.23 ± 0.21 ng/dL vs. 1.38 ± 0.30 ng/dL, p-value 0.0002) compared to normal-weight participants. We observed a positive correlation between BMI and TSH (p-value 0.002) and FT3 (p-value < 0.001), and a negative correlation between BMI and FT4 (p-value 0.003). Most of the obese children were euthyroid (71.01%), with 27.54% showing subclinical hypothyroidism and 1.45% showing overt hypothyroidism. Multivariable linear regression analysis revealed that with a one unit increase in BMI, FT3 increased by 0.032 ± 0.011 pg/mL (p-value 0.004), FT4 decreased by 0.010 ± 0.004 (p-value 0.017 ng/dL, and TSH increased by 0.104 ± 0.044 µIU/mL (p-value 0.020). Conclusions: The significant association between BMI and thyroid hormone levels underscores the necessity for routine thyroid function monitoring in obese paediatric populations. The early detection and management of thyroid dysfunction may enhance health and well-being outcomes in obese children and adolescents.