Abstract Background and aims We aimed to assess bone mineral density (BMD) in geriatric patients with hyperthyroidism caused by TNG. Materials and methods Bone mineral density was measured at the lumbar spine and proximal femur, using dualX-ray absorptiometry (DXA) in 90 patients with TNG (mean age; 69.2± 4.4 years) and compared with those in 42 age-matched healthy subjects (mean age; 68.40 ± 4.3 years). Serum levels of TSH, fT3, fT4, 25-OH vitamin D and PTH were measured. Results BMD was significantly lower at total spine (0.904 ± 0.1 vs. 1.114 ± 0.1 g/cm2 ) and total hip (0.850 ± 0.1 vs. 1.079 ± 0.1 g/cm2 ) in male patients with TNG in comparison to the healthy men (p = 0.001, p\0.001). Postmenopausal women with TNG had lower BMD measurements at total lumbar spine (0.754 ± 0.1 vs. 0.870 ± 0.2 g/cm2 , p\0.001) and total hip (0.765 ± 0.1 vs. 0.831 ± 0.2 g/cm2 , p\0.001) in comparison to the healthy women. T scores of total lumbar spine and hip were lower in patients with subclinical hyperthyroidism compared to the control group, respectively (-1.9 ± 1.7 vs -0.8 ± 1.8, p = 0.007; -1.09 ± 1.2 vs. -0.02 ± 1.6, p = 0.001). While serum levels of fT3 and fT4 revealed a negative correlation with T score of BMD measurements at the total spine and hip, TSH levels were positively correlated. We did not find a difference in serum calcium, phosphorus, 25-OH vitamin D and PTH levels between the two groups (p[0.005). Conclusion Geriatric patients with hyperthyroidism secondary to TNG had reduced BMD at the total spine and hip. Thus, we suggest to investigate bone mineral density in geriatric patients with TNG.