Head circumference, height, bone age and weight in 103 children with congenital hypothyroidism before and during thyroid hormone replacement.

Head circumference, height, bone age and weight were studied in 103 children with congenital hypothyroidism before and up to 8 years of thyroid replacement therapy. The patients were divided into 4 groups according to the age at start of treatment: group I (diagnosed by neonatal screening): less than 2 weeks (n = 55); group II: 1-3 months (n = 7); group III: 4-12 months (n = 15); group IV: greater than 1 year of age (n = 26). Before treatment, group I showed a head circumference significantly larger than normal and a delay in bone maturation in the presence of normal length and weight. In the other groups length as well as bone age were significantly lower than normal, head circumference, in contrast, was normal (groups II and III) or even increased (group IV). During therapy, head circumference and bone age of group I became normal as were length and weight from the beginning. In the other groups, therapy led to a further increase of head size resulting in a mean head circumference significantly larger than normal during 8 years of observation in group IV. There was a catch-up of height, bone age and weight in groups II, III and IV; mean height of late treated children (group IV), however, remained significantly lower than normal even after 8 years of therapy. - Our study shows that congenital hypothyroidism is associated with increased head circumference, either absolutely or in relation to stature. Thyroid hormone therapy resulted in a normalization of head growth when treatment was initiated early, and in a further increase when treatment was started late. There was a catch-up of height, bone age and weight; complete normalization, however, occurred only in those children treated before one year of age.