Congenital hypothyroidism is associated with a smaller caudate nucleus, lower levels of attention, and lower behavior ratings, even in children who started treatment as infants, according to research presented at the annual meeting of the American Thyroid Association.
Santhosh Sekharan, a pharmacology research student at the Hospital for Sick Children, Toronto, analyzed brain scans and test scores of 15 children (aged 10-15 years) with congenital hypothyroidism. The hypothyroidism was caused by thyroid dysgenesis in 11 patients (including 4 with athyrotic dysgenesis and 7 with ectopic thyroid dysgenesis) and hormonal dysgenesis in 4 patients. Treatment for this cohort started at a mean age of 13 days, at a median starting dose of 19.4 mcg/kg of thyroxine (T4). There were 17 control children, for whom prematurity and head injury were exclusion criteria.
The participants and the control group underwent testing for intelligence, memory, and attention, as well as a 1-hour MRI scan, and each mother completed questionnaires assessing her child's behavior.
MR scans revealed that the left and right caudate volumes of the children with congenital hypothyroidism were significantly smaller than were those of the control children. However, among the hypothyroid participants, caudate volume did not vary according to the etiology of the hypothyroidism (athyrotic dysgenesis, ectopic thyroid dysgenesis, or hormonal dysgenesis). Nor did caudate volume differ by age at the inception of treatment, Mr. Sekharan reported.
Greater left-caudate volume predicted higher attention scores, whereas greater right-caudate volume was associated with better scores on parental ratings of behavior.
“Because thyroid hormone is so crucial for early brain development, children with [congenital hypothyroidism] often have severe brain damage and may suffer mental retardation,” he said. “Thankfully, with the advent of newborn screening, these kids can be diagnosed and, more importantly, treated right after birth.”
Congenital hypothyroidism affects 1 in 2,500 newborns in North America and can result from thyroid dysgenesis, hormonal dysgenesis, or abnormal regulation of thyroid hormone synthesis, he noted.