Reference range of thyroid hormones in healthy school-age children: country-wide data from India

Abstract

Objective: This study was planned to obtain normative data of thyroid functions in school-age children from different regions of India. Design and Methods: Students from 36 schools involving 13 states across four geographical zones of India were evaluated for goiter. Subjects who consented, underwent evaluation for serum FT3, FT4, TSH, anti-TPO antibodies and thyroid ultrasound. From this, a “reference population” was obtained by excluding those with personal or family history of thyroid disease, use of thyroid medications, goiter, hypoechogenicity or nodularity on ultrasound or positive anti-thyroid antibodies. Results: Of 24,685 students clinically evaluated, 8665 formed part of the study. The reference population comprised 5343 subjects. The mean, median, 3rd and 97th percentiles of FT3, FT4 and TSH for each year (6–17 years) were obtained. Conclusions: This community based study in Indian school-age children provides reference intervals for thyroid hormones and evidence against narrowing the TSH reference range.