Bone metabolism in children with congenital hypothyroidism--a longitudinal study.

In order to evaluate the effect of thyroid replacement therapy on bone metabolism in congenital hypothyroid children, we studied 23 (10 girls and 13 boys) consecutive patients. Their age ranged from 3 to 8 weeks. One of these patients had familiar dyshormonogenesis, 21 had ectopic glands and one hemiagenesis. As a control group, we studied 46 sex- and age-matched healthy newborns. Before the beginning of therapy, the hypothyroid patients showed higher values of calcium (2.78 +/- 0.04 vs 2.65 +/- 0.07 mmol/l; p < 0.05) and of 1,25-dihydroxy-vitamin D (159.7 +/- 31.6 vs 90.5 +/- 33.1 ng/l; p < 0.01), while they showed lower values of osteocalcin (1.9 +/- 0.8 vs 2.9 +/- 0.9 ng/ml; p < 0.01) than controls. After 3 months of therapy, we found a complete normalization of all these parameters and a progressive increase of osteocalcin. Our data show that in congenital hypothyroid children there are abnormalities in calcium metabolism which seem to be transient and reversible after L-thyroxine replacement therapy.