[Growth in children with impairment of thyroid gland function]

Changes of thyroid function affect beyond doubt the growth rate and bone maturation. In particular thyroid hypofunction during the first months of life leads not only to irreversible disorders of the development of the CNS but causes also a significant impairment of growth. In older children and adolescents with a more long-lasting thyroid dysfunction milder growth disorders without mental retardation were observed. The effect on growth by thyroid hormones takes place at the level of metabolic processes of every single cell and in particular at the level of growth cartilage. The purpose of our investigation was to test the relationship between the production of the growth factor somatomedin C (insulin growth factor-1) and the thyroxine level in children with congenital hypothyroidism revealed during neonatal screening.

The somatomedin (SMA) activity was examined in 13 neonates aged 10-23 days with confirmed CH. Total thyroxine (T4) and thyroid stimulating hormone (TSH) were estimated using commercial RIA kits. SMA was assessed by Hall's biological method in Schimpff and Donnadie's modification. The control group comprised 10 healthy children aged 8-20 days and 10 children aged 29-94 days. SMA was examined before and then one month after the onset of L-thyroxine treatment. Before treatment the author found in 10-23 old infants with congenital hypothyroidism significantly lower SMA values than in controls (p < 0.01 at the 1% level of significance). During treatment the SMA values in both groups were equal.

Early hormonal substitution therapy, i.e. as soon as possible after delivery, is essential in children with congenital hypothyroidism not only for normal growth of the CNS but also for normal continuous growth.