Longitudinal changes of bone density and bone resorption in hyperthyroid girls during treatment

Low bone mineral density (BMD) and increased bone turnover are common featu res of untreated hyperthyroidism in adult patients. The effect of treatment on BMD is still controversial. BMD and bone metabolism in hyperthyroid chi ldren have not been thoroughly investigated. Ln the present study, we measu red spinal and whole body BMD by dual-energy X-ray absorptiometry in a grou p of 13 girls (aged 5.0-14.9 years) at diagnosis of hyperthyroidism, The bo ne resorption rate was assessed by urine measurement of N-terminal telopept ide of type I collagen (NTX), Hyperthyroid patients have been studied longi tudinally during treatment. BMD values and NTX urine concentrations have be en also determined in 155 healthy Caucasian girls (aged 2.4-24.2 years). Sp inal and whole body bone density measurements were significantly lower comp ared with healthy controls in untreated hyperthyroid girls, after correctio n for differences in age and anthropometric measurements (p less than or eq ual to 0.033), Bone density measurements obtained after 12 and 24 months of treatment were no longer different from those of healthy girls. NTX urine levels at diagnosis of thyrotoxicosis were significantly higher than those found in healthy controls (p < 0.0001); 6 months after treatment, the urine levels did not show significant differences, and they remained stable afte r 12 and 24 months of therapy, Inverse correlations at diagnosis were found between serum-free thyroxine (FT4) serum levels and spinal (r = -0.42) and whole body bone density (r = -0.41); FT4 and free triiodothyronine serum l evels directly correlated with the NTX concentration (I = 0.77, and r = 0.7 1, respectively), Zn conclusion, the results of the present study demonstra te that low bone density values and high bone resorption rates are found in hyperthyroid children and adolescents at diagnosis of the disease. Our dat a also demonstrate that antithyroid treatment is able to reduce dramaticall y the bone resorption and to increase significantly both spinal and total b ody BMD, granting physiologic conditions for the achievement of the best ob tainable peak bone mass.