High prevalence of extrathyroid malformations in a cohort of Brazilian patients with permanent primary congenital hypothyroidism.

The objective of this study was to evaluate the prevalence of major congenital malformations in a cohort of children with permanent primary congenital hypothyroidism (PCH). This cross-sectional study was conducted in 76 consecutive, unselected children with PCH recruited from a district hospital outpatient clinic. Malformations were identified by clinical examination. The prevalence of major congenital malformations in these patients was compared with the prevalence of malformations in children born at Hospital de Clínicas de Porto Alegre (HCPA). The etiology of hypothyroidism was established by scintigraphy and ultrasonography. Hypothyroidism was caused by thyroid dysgenesis in 67 patients (one case of hemiagenesis, 24 of ectopia, and 42 of agenesis); the gland was normally located and shaped in nine patients. Ten patients (13.2%) had major congenital malformations (1,316/10,000 patients), mostly cardiac. Malformations were observed only in patients with dysgenesis: thyroid agenesis (n = 7) and sub-lingual ectopic thyroid (n = 3). The prevalence of malformations was significantly higher (RR = 2.6; CI 95%: 1.3-4.8; p = 0.005) in this group than in HCPA newborns (509/10,000 patients). In conclusion, a high rate of extrathyroid congenital malformations, mostly cardiac, was found for patients with permanent PCH, especially thyroid dysgenesis. The present data support the existence of an association between CH and increased prevalence of congenital malformations.