Increased bone mineral density in patients with chronic hypoparathyroidism

Bone mineral density (BMD) has been shown to be increased in postmenopausal females with postthyroidectomy hypoparathyroidism, but it is not known whether similar gains occur in patients with idiopathic hypoparathyroidism. In this study, we measured the BMD of lumbar spine and proximal femur in 14 patients, 8 with idiopathic hypoparathyroidism and 6 with postthyroidectomy hypoparathyroidism, using dual-energy x-ray absorptiometry. Their age ranged from 23-57 yr old, with a mean of 42.5 yr. The results showed that patients with hypoparathyroidism had a higher BMD than the normal age- and sex-matched population. This was particularly evident at the lumbar spine (L2-L4), with positive Z-score of 1.93 +/- 1.03, whereas Z-score at the femoral neck was 1.14 +/- 0.62 SD. Subgroup analysis showed that those with postthyroidectomy hypoparathyroidism had a mean lumbar spine BMD of 1.434 g/cm(2) and femoral neck BMD of 1.026g/cm(2), compared with a mean BMD of 1.364 g/cm(2) and 1.022 g/cm(2) at spine and hip, respectively, for those with idiopathic hypoparathyroidism. Statistical analysis did not reveal any significant difference in the BMD, T-score, and Z-score of the bone, at these two sites, between the two groups. In conclusion, the state of chronic hypoparathyroidism is associated with increased BMD, especially at the lumbar spine. Those with idiopathic hypoparathyroidism have a similar degree of increase in BMD as those with postthyroidectomy hypoparathyroidism.