[Bone demineralization and elevation of serum osteocalcin concentrations in young children with hyperthyroidism]

Bone mineralization and serum osteocalcin level were evaluated in 15 children with Grave's disease. Two groups were constituted according to the presence (group I: n = 9) or absence (group II: n = 6) of a severe bone demineralization. A spontaneous fracture and a collapsed vertebra were found in one group I patient. Patients in group I were younger than in group II (8.3 +/- 4.9 vs 11.5 +/- 4.3 yrs). One patient in group II and six in group I were prepubertal with advanced bone age and increased growth velocity. Osteocalcin measurement (Oc) was performed in 10 patients (group I: n = 6; group II: n = 4) at the time of biological hyperthyroidism. The six patients with bone demineralization had elevated Oc levels. In group II, two patients had normal Oc levels and two had elevated Oc levels. In treated patients with good control of hyperthyroidism, all group II patients except one, had normal serum Oc levels and bone mineralization remain normal (n = 5) after 0.6 to 4.6 yrs of follow-up. In group I patients, although height velocity was normal, elevated (n = 4) or slightly elevated (n = 1) serum Oc levels and severe bone demineralization (n = 7 cases) persisted after 0.5 to 3 yrs of good control of the hyperthyroidism. Although the method used for measuring bone mineralization is potentially less precise than bone densitometry and not all the patients had serum osteocalcin measurements at the same time of the illness, our results emphasize that skeletal demineralization may be particularly marked in young children with Grave's disease and should be carefully evaluated.