Abstract
Increased bone turnover and loss of bone mass in adult patients with hyperthyroidism is well documented, but bone manifestations in children with hyperthyroidism are poorly understood. We evaluated cortical bone mineral density (BMD) and bone metabolic markers in two boys and five girls, aged 5.7~16 yrs (12.2 ± 3.7 yrs) with hyperthyroidism before and during treatment. BMD (ΣGS/D) was assessed by computed X-ray densitometry in the second metacarpal bone of the left hand. The %BMD (percentage for expected ΣGS/D of age- and sex-matched standard) before treatment was 90.5 ± 8.5% (M ± SD), which was lower than normal children (p<0.05). After 6 months of treatment, %BMD increased to 95.9 ± 9.5%, showing partial restoration. Basal levels of urinary N-telopeptides of collagen type 1 (NTx) before treatment were markedly high, but decreased rapidly during treatment towards the normal range. We also found a transient rise in NTx on day 4 of treatment before the decrease. Basal levels of serum bone alkaline phosphatase were as high as the upper limits of the reference ranges in pubertal children, slightly decreasing for the first two weeks of treatment, increasing transiently for a few months and declining thereafter. We demonstrated decreased BMD in children with hyperthyroidism for the first time. Bone resorption rapidly ameliorated, and accelerated bone formation persisted for a few months after normalization of thyroid function, while BMD improved at 6 months' evaluation, as reported in adult patients. We also found a transient increase in bone resorption markers and initial suppression of bone formation markers before the amelioration. A longer period of follow up with more patients is needed to clarify how the mechanism of bone metabolism is affected by thyroid function.
