Osteitis fibrosa cystica

Osteitis fibrosa cystica is a skeletal disorder resulting in a loss of bone mass, a weakening of the bones as their calcified supporting structures are replaced with fibrous tissue, called peritrabecular fibrosis, and the formation of cyst-like brown tumors in and around the bone. It is caused by hyperparathyroidism, a surplus of parathyroid hormone from over-active parathyroid glands, which activates bone-breaking cells called osteoclasts through a process called osteoclastic bone resorption, releasing minerals such as calcium into the bloodstream. Symptoms follow from both the general softening of the bones and the excess calcium in the blood, and include bone fractures, kidney stones, nausea, a moth-eaten appearance in the bones, appetite loss and weight loss. The disease is currently detected through a combination of blood testing, X-rays and tissue sampling. Before 1950 roughly half of hyperparathyroidism cases in the United States progressed to this disease, but improved early detection has made it increasingly rare in developed nations.