Screening for congenital hypothyroidism

OBJECTIVE: To review the screening program for congenital hypothyroidism in the Riyadh Al-Kharj Hospital Programme, Riyadh, Kingdom of Saudi Arabia, and to investigate the clinical and biochemical characteristics of affected infants.

METHODS: The study was carried out from 1985 to 2000 in the Clinical Chemistry Division, Department of Pathology, Riyadh Armed Forces Hospital, Kingdom of Saudi Arabia. Laboratory data and case notes of infants diagnosed with congenital hypothyroidism were used to supply the relevant data and information.

RESULTS: One hundred and twenty-one thousand, four hundred and four infants were screened over a period of nearly 15 years. The overall incidence of congenital hypothyroidism was 1:2759 live births with a female: male ratio of 1.8:1. The incidence in a rural satellite hospital was 1:1538. No seasonal variation was observed. Apart from jaundice, signs and symptoms of congenital hypothyroidism were rarely present in the neonatal period. The neonatal and maternal parameters of affected infants did not differ significantly from those of other infants. The predominant cause of congenital hypothyroidism was athyreosis (45%), followed by thyroid ectopia (24%) and dyshormonogenesis (17%). The mean age at the start of treatment of infants diagnosed in the screening program was 10.3 days.

CONCLUSION: The screening program based on initial measurement of thyroid stimulating hormone in cord blood captures 97% of infants born in the Riyadh Al-Kharj Hospital Programme. The incidence of congenital hypothyroidism was 1:2759 live births with a female:male ratio of nearly 2:1. Congenital hypothyroidism infants had similar neonatal parameters as other infants. No seasonality in the incidence of congenital hypothyroidism was observed. In general, affected infants were started on thyroxine very soon after birth.