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

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 ± 10.7 yr) 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), (48.2± 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 (x² = 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. (authors)