Congenital hypothyroidism. Aetiological and clinical aspects.

In 67 patients with congenital hypothyroidism radioiodide tests, including thyroid scintigraphy, were used to study the aetiology. Athyrosis was found in 5 boys and 16 girls (31%), maldevelopment of thyroid gland in 1 boy and 2 girls (5%), ectopic gland in 4 boys and 20 girls (36%), and dyshormonogenesis in 7 boys and 12 girls (28%). In the last-mentioned group, organic binding of iodide was defective in 13; in the 9 families studied there was evidence of autosomal recessive inheritance. Duration of pregnancy had exceeded 42 weeks in 20 (32%) out of 63 pregnancies. Birthweights in 22 out of 64 patients and birth lengths in 21 out of 61 were over the 90th centile for the duration of gestation. At the time of diagnosis a goitre was observed in only 3, and some thyroid tissue in 2 of the 19 patients with dyshormonogenesis, but a goitre frequently appeared later, particularly at puberty. Neurological defects were found in 33%, and mental retardation in 44% of the patients. The prognosis was best in the children with a persisting ectopic thyroid gland and poorest in those with defective organic binding of iodide. The importance of early diagnosis of hypothyroidism is again emphasized.