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.

Ultrasonography is an accurate method to establish the presence of dysgenesis and might be used as the first imaging tool in patients with CH, whereas scintigraphy should be used mainly to distinguish agenesis from ectopia. Further examination is required to differentiate permanent CH with a normally located and shaped gland from transitory hypothyroidism.

Maternal schooling, number of visits during the first year of life and baseline T4 levels were the main predictors of cognitive outcome in this cohort of patients.

The use of hemoperfusion with a charcoal filter appears to be a very important therapeutic tool for the treatment of acute and severe forms of thyrotoxicosis due to l-thyroxine intoxication.

The incidence of missed congenital hypothyroidism diagnoses in this neonatal screening program based on the TSH approach was low and acceptable. Nevertheless, with the proposed strategy, the risk of false negative results can be reduced without significant impact on the overall cost of the screening program.