Hypoparathyroidism counteracts risk factors for osteoporosis

Although increased bone density has been reported in patients with hypoparathyroidism, it is not known whether hypoparathyroidism can overcome the influence of risk factors for osteoporosis and whether the increased bone density is uniform throughout the entire skeleton or greater in certain regions depending on the bone composition and location. In the current study, bone density was measured in patients with postsurgical hypoparathyroidism and risk factors for osteoporosis. Bone mineral density was determined in eight patients with postsurgical hypoparathyroidism, one with idiopathic hypoparathyroidism, and two with pseudohypoparathyroidism in eight different areas of the skeleton using well established methods: single photon absorptiometry of the radius, dual energy x-ray absorptiometry of the spine, hip, and the whole skeleton, and quantitative computed tomography of the spine. Risk factors for osteoporosis were documented in each subject. The data showed that despite the presence of 1-4 risk factors for osteoporosis, patients with postsurgical hypoparathyroidism had bone mineral density above the normal mean in most locations. The locations with the highest increment were the Ward's triangle and the trochanter area of the proximal femur (dual energy x-ray absorptiometry) (Ward's: Z score + 1.59 +/- 0.57, P < 0.03; trochanter 1.31 +/- 0.42, P < 0.02). The elevation of bone density was not observed in one patient with idiopathic hypoparathyroidism, and variable results were observed in two patients with pseudohypoparathyroidism. Based on these findings, in postsurgical hypoparathyroidism, the bone mineral density is above the normal mean despite the presence of risk factors for osteoporosis, and both cortical and trabecular bone are affected.