Impact of body mass index on thyroid functions in Indian children

Abstract

Objective: There is controversy about the relation of thyroid functions and body mass index. The present study was aimed to assess the relationship between thyroid function and body mass index in Indian school children. Design: Population survey. Patients: Data were collected from 25 schools in 19 cities across five different geographical zones of India. Children, who consented, were evaluated for anthropometry and blood tests. Children were categorized as overweight and obese based on standard BMI criteria. Measurements: Serum samples were analyzed for free T3, free T4, TSH and anti-TPO antibodies. Results: A total of 13 691 children in the age group of 5–18 years formed the study population. The mean age and mean BMI were 11.9 ± 3.0 years and 18.48 ± 3.89 kg/m² respectively. Among these, 2119 (15.5%) children were overweight and 536 (3.9%) were obese. Subclinical hypothyroidism was present in 943 (6.9%) children. FT3 and TSH levels increased and FT4 levels decreased with increasing BMI in euthyroid boys and girls. Prevalence of SCH was significantly higher in obese/overweight children (9.0%, vs. 6.5%; P = 0.034) as compared with normal BMI children. Conclusions: Serum FT3 and TSH were positively while FT4 was negatively associated with BMI in apparently healthy euthyroid children.