Revisiting early hypothyroidism screening in infants with Down syndrome

OBJECTIVE: To identify if the incidence of hypothyroidism in infants with Down syndrome is higher than previous childhood estimates (15%) when examined prior to the standard retesting at 6 months of age. STUDY DESIGN: A retrospective observational cohort study of 122 children with Down syndrome admitted to a university-based birthing hospital between May 2000 and March 2012. Demographic data (for example, date of birth, gender, gestational age, inborn) and diagnostic data (Down syndrome, congenital heart disease and gastrointestinal disease) were cross-linked with thyroid hormone laboratory tests (total thyroxine, free thyroxine and thyroid stimulating hormone) to determine incidence of identified hypothyroidism and thyroid testing prior to 4 months of age (n=80). RESULT: In all, 32.5% were found to have any hypothyroidism. Of these, 14 were primary hypothyroidism (17.5%) needing supplemental T4 therapy, 12 were compensated hypothyroidism (15%) and euthyroid was identified in 54 infants (67.5%). CONCLUSION: Despite normal newborn screens, the incidence of any hypothyroidism (early compensated hypothyroidism and primary hypothyroidism) was higher than previously reported.