Incidence of congenital malformations in congenital hypothyroidism

Abstract

Introduction: We investigated the frequency and types of congenital malformations in infants with congenital hypothyroidism (CH) detected by neonatal screening in four northeastern regions of Italy. Methods: Newborn dried blood specimens were collected at 3–7 days of age. Thyroid hormone (T4) and thyroid stimulating hormone (TSH) were measured by radio-immunoassay. Results: 235 infants with CH were identified among 745 801 screened infants (1:3174). 22 infants (9.4%) had congenital anomalies, as compared to an incidence of 1.8% for congenital anomalies in the general population. The infants with CH and congenital anomalies had significantly lower values for blood T4, birth weight and gestational age. Discussion: This study confirms other data indicating that congenital malformations are substantially more frequent among infants with CH than expected. The presence of these malformations, which often produce clinical complications in the neonate, should not delay collection of the neonatal screening specimen or the start of treatment in infants found to have CH.