ESPE Abstracts

Background: Primary care pediatricians (PCPs) use thyroid function tests (TFT) as screening tests in children and adolescents with various health complaints. Thus, it is crucial to evaluate the results according to appropriate cut-offs individualized to the child characteristics. Such references values, which are missing in the pediatric age group, are needed for proper evaluation of the thyroid functions.

Objective and hypotheses: To determine normal TSH levels in a large cohort of healthy children individualized according to their age, sex, BMI and ethnicity.

Method: Data was collected from the database of Clalit Health Medical Organization (CHMO) ensuring more than 1.3 million children. 75,857 children aged 5 to 18 years without previous thyroid disease or treatment, who had TFT evaluation during 2012–2014 were included in the study. Data evaluated included: age, gender, TSH, FT4 and FT3 levels, BMI SDS (according to WHO norms), ethnicity and dispensed medications.

Results: TSH levels were significantly higher in boys compared to girls: median 2.21 mIU/L (normal range 0.83–5.25) vs 2.11 mIU/L (0.89–5.29), P<0.0001. TSH levels were found to vary significantly according to ethnicity; TSH Ievels in the Jewish population were significantly lower compared to the Israeli Arab population: median 2.14 mIU/L (0.85–5.14) vs 2.22 mIU/L (0.84–5.85), P<0.0001. BMI was found to significantly effect TSH levels with levels increasing as weight diverge from the normal range; median levels were 2.13 mIU/L (normal range 0.74–5.13), 2.04 mIU/L (0.79–5.05), 2.14 mIU/L (0.88–5.45), 2.37 (0.95–5.74) for children defined as underweight, normal weight, overweight and obese respectively. Age did not significantly affect TSH distribution.

Conclusion: Our results in this uniquely large cohort show that the normal range of TSH in children is affected by gender, weight and ethnicity. Reference values should be thus individualized and modified accordingly. Such modifications will improve future clinical decision-making and treatment.