Thyroid Stimulating Hormone Level at Diagnosis as a Predictor of Persistent Subclinical Hypothyroidism in Children with Down Syndrome

To evaluate subclinical hypothyroidism in a cohort of children with Down syndrome and identify a TSH level at the time of diagnosis to predict persistent hypothyroidism.

192 children (age <3 years) with Down syndrome, registered in the Genetic Clinic of a referral tertiary care Hospital from 2010 to 2015 were evaluated with thyroid function test at initial visits and subsequently based on standard protocol. Children with subclinical hypothyroidism were evaluated at 3 years of age after discontinuation of thyroxine for 3 months.

47 (24.5%) children had elevated TSH and among them 43 (91.5%) had subclinical hypothyroidism. Among the subclinical hypothyroidism group, 25 (73.5%) had transient hypothyroidism and 9 (26.5%) persistent hypothyroidism. Initial TSH level at the time of diagnosis was higher in persistent hypothyroidism group as compared to transient group (P= 0.003). The best cut-off level for prediction of persistent hypothyroidism for initial TSH level was 11.6 mIU/L.

Subclinical hypothyroidism, especially transient, is the commonest form of thyroid dysfunction in children with Down syndrome. The initial TSH level may help to predict the possibility of persistence of hypothyroidism.