Higher incidence of thyroid agenesis in Mexican newborns with congenital hypothyroidism associated with birth defects.

Background: Congenital hypothyroidism (CH) is the most common endocrine system disorder in newborns. Ectopic thyroid and agenesis are the most frequent thyroid structural malformations. Several reports have shown that CH is associated with birth defects (BD) ranging from congenital heart disease to ocular and gastrointestinal anomalies.

Aims: We investigated how many and what types of BD were associated with CH in Mexican children.

Study Design: Cross-sectional study conducted in patients with confirmed CH.

Setting: Highly specialized government pediatric center in Mexico City.

Subjects: We included 212 patients with permanent CH identified by newborn screening.

Results: We found that 24% of patients with CH also had BD, and that there was a higher prevalence of thyroid agenesis in the group of patients with CH associated with BD (CH+BD) versus the isolated CH group (p=0.007). There were more females than males in both groups. The most common BD were congenital heart diseases, especially those of the atrial septum, followed by patent ductus arteriosus, found as a single malformation or as part of a complex congenital heart disease. In this study, we found Hirschsprung disease, Beckwith-Wiedemann syndrome, Pierre Robin sequence, Albright's osteodystrophy, VATER association, and frontonasal dysplasia associated with CH.

Conclusions: In this study population, there was a high prevalence of BD in patients with permanent CH. Thyroid agenesis was the main etiological cause of CH in patients with associated congenital malformations. The high prevalence of CH+BD underlines the need for a comprehensive clinical diagnostic approach of the patients with CH.