Intellectual development in children with congenital hypothyroidism in relation to recommended thyroxine treatment.

The relationship between the treatment serum thyroxine level and intellectual development at 2 and 6 years was investigated in 46 Norwegian children with congenital hypothyroidism identified by neonatal screening. The level of serum thyroxine during the first 2 years was positively correlated with the Mental Development Index at 2 years of age (Bayley Scales of Infant Development) and the Verbal IQ at 6 years of age (Wechsler Preschool and Primary Scale of Intelligence). Children with a mean serum thyroxine level greater than 180 nmol/L (14 micrograms/dl) during the first year had a significantly higher Mental Development Index at 2 years and Verbal IQ at 6 years than children with serum thyroxine values less than 129 nmol/L (10 micrograms/dl). Boys had a lower Mental Development Index at 2 years of age than girls (86.9 vs 105.1; p less than 0.001) and a higher frequency of elevated serum levels of thyroid-stimulating hormone during the first year (p = 0.001). No signs of toxic effects of a high hormone level at the time of IQ assessment were detected. However, high serum levels of thyroxine at ages 2 to 4 years in girls were related to lower Performance IQ at age 6 years. The results demonstrate that the serum level of thyroxine is of importance in relation to intellectual development. Thyroxine levels above the upper reference range during the first 2 years were related to best intellectual development at 2 and 6 years.

Peroxisomal dysfunction in a boy with neurologic symptoms and amaurosis (Leber disease): clinical and biochemical findings similar to those observed in Zellweger syndrome.

A boy with psychomotor retardation and Leber congenital amaurosis, sensory hearing loss, and hepatomegaly is reported. Accumulation of bile acid precursors and very long chain fatty acids together with impaired biosynthesis of plasmalogens in cultured fibroblasts (similar to those in the cerebrohepatorenal syndrome of Zellweger) were detected, but the clinical picture was distinctly different. Defective oxidation of phytanic acid was measured in fibroblasts. The virtual lack of peroxisomes in a liver biopsy specimen lends further support to the contention that at least some patients with Leber congenital amaurosis may have one of the recently defined "peroxisomal disorders." The biochemical findings indicate the possibility of prenatal diagnosis.