ESPE Abstracts

Objective: To determine the prevalence of congenital hypothyroidism (CH) in children with dry bloodspot TSH (_b-TSH) between 5 and 10 mIU/l in neonatal screening and evaluate their thyroid function evolution.

Methods: Retrospective study of thyroid function in children born from 2003 to 2010 with _b-TSH between 5 and 10 mIU/l who were put on treatment in the first two years of life due to serum TSH≥10 mIU/l. The prevalence of CH was determined, as well as the permanent congenital hypothyroidism (PCH) frequency among those born at term and healthy, who had been followed for at least 6 months after treatment withdraw. PCH was considered when the treatment was reintroduced due to steadily TSH≥10 mIU/l. Thyroid scintigraphy with technetium-99m (^99mTc) was done for etiologic investigation.

Results: From 380,741 neonates screened, 3,713 (1.0%) had _b-TSH between 5 and 10 mIU/l, of which 339 (9.1%) had CH. Children born preterm (32), with neonatal anoxia (2) or genetic syndromes (13) or hyperthyroid mother (1), as well as 35 individuals who were not followed for 6 six months after thyroxin withdraw were excluded in the late thyroid function evaluation. From the remaining group of 256 children (152 males), 70 (27.3%) had PCH among which 4 thyroid dysgenesis (2 hemiagenesis, 1 lobe hypoplasia and 1 thyroid hypoplasia) and 8 goitres. Serum FT4 levels in the initial neonatal evaluation were lower in the PCH group (P=0.002). Other relevant findings were that 22.6% of children took more than 4 months to develop CH and 25.7% of those with PCH had the diagnosis of the permanent deficiency only after 4 months of treatment withdraw.

Conclusion: The _b-TSH screening-test cutoff of 5 mIU/l, along with clinical and laboratory follow-up allowed the early detection of 339 CH and 70 permanent hypothyroid children that would have been missed if the current _b-TSH cutoff of 10 mIU/l was used.