Primary hyperparathyroidism: pathophysiology and impact on bone

Primary hyperparathyroidism has been associated with bone loss, especially at cortical skeletal sites. Results from studies evaluating the mineral den sity of cancellous bone have been more difficult to interpret. Most densito metry studies support the concept that the parathyroid hormone appears to b e catabolic at cortical sites and may have anabolic effects at cancellous b one sites. Studies completed to date, however, have been limited by design, definitions of fracture and inadequate control groups. Primary hyperparath yroidism is now increasingly being detected during the asymptomatic phase. The need for parathyroidectomy has been questioned-in such patients because there may be no disease progression in the absence of surgery. Medical man agement of primary hyperparathyroidism has to date been limited to estrogen replacement therapy in postmenopausal women. Identification of the calcium receptor has improved our understanding of calcium homeostasis, and signif icant reductions in calcium receptor levels have been detected in parathyro id adenomas. Thus, a new class of therapeutics may include the calcimimetic agents. Bisphosphonates are also currently being evaluated with regard to their impact on fracture prevention and their beneficial effects on bone mi neral density.