Changes of bone mass in patients with Graves' hyperthyroidism before and after 131I therapy based on CT spectral imaging

Abstract

Objective To investigate the value of CT spectral imaging to evaluate bone mass in patients with Graves' hyperthyroidism, and the changes of bone mass before and after 131I therapy. Methods Sixty-eight patients(13 males, 55 females; age 40.6±10.7yr) with Graves' hyperthyroidism who received 131I therapy from June to October 2015 were involved in our study. The bone mineral density(BMD) of lumbar was obtained by dual energy X-ray absorptiometry(DXA), and the calcium-water concentration of L3 was measured by CT spectral imaging before 131I therapy. Pearson correlation analysis and linear regression were performed to explore the relationship between them. All clinical data were collected to assess the efficacy of 131I therapy after 6 months. CT spectral imaging was repeated, in order to compare the changes of bone mass using comparative t-test. Results Of these patients with Graves' hyperthyroidism, 30.9% (21/68) patients with osteopenia and 10.3%(7/68) patients with osteoporosis were diagnosed according to the results of BMD by DXA. The calcium (water) densities of L3 were (64.33±14.65), (48.29±4.45) and (41.65±1.21) g/cm3 in patients with normal bone mass, bone loss and osteoporosis, respectively. The differences between the three groups were statistically significant (χ2=35.811, P<0.001). The bone mineral density of L3 were (1.252±0.305), (1.103±0.254) and (0.539±0.066) g/cm3 in patients with normal bone mass, bone loss and osteoporosis, respectively. The differences between the three groups were statistically significant (F=12.968, P<0.001). The calcium-water concentrations of L3 (g/cm3) were highly correlated with BMD values (g/cm2) of lumbar determined by DXA(r=0.794, hypothesis testing standard α=0.01, t=10.605, P<0.001). Equation of linear regression: the calcium-water concentration of L3=24.485+34.529 BMD value of lumbar. Furthermore, after 131I therapy, the calcium-water concentrations of L3 increased(t=7.86, P<0.001) in the cured group of patients. But there weren't significant difference in the uncured group of patients(t=2.29, P=0.062). Conclusions CT spectral imaging can be used to evaluate bone mass in patients with Graves' hyperthyroidism. Bone mass can be improved with remission of hyperthyroidism after 131I therapy. Key words: Graves disease; Hyperthyroidism; Tomograp, X-ray computed; Bone mass; Radionuclide therapy; Iodine Radioisotopes