Osteitis fibrosa is a complication of hyperparathyroidism (excess parathryroid hormone production) in which bone becomes softened, deformed and may develop cysts.

There are four parathyroid glands in the neck. They produce parathyroid hormone, which helps control calcium levels in the body. Sometimes they produce too much parathyroid hormone (hyperparathyroidism). In these cases, one gland may develop a growth (80% of cases);or all 4 glands may enlarge (15% of cases). Rarely, parathyroid cancer may cause the condition.

Hyperparathyroidism is most common in women over 60. Genetic changes cause it, and it sometimes runs in families. Neck radiation increases the likelihood of developing this disorder. Parathyroid hormone increases bone "turnover" (metabolism) and may soften it.

Before 1950, about half of people diagnosed with hyperparathyroidism had osteitis fibrosa cystica. Now it is uncommon (less than 10% of people with hyperparathyroidism) because patients are diagnosed earlier and have milder elevations of calcium. People with severe hyperparathyroidism, or those who have parathyroid cancer, are more at risk for developing osteitis fibrosa cystica.

Osteitis fibrosa cystica may cause bone pain or tenderness. There may be fractures (breaks) in the arms, legs, or spine, or deformities (bowing of the bones). Hyperparathyroidism itself may cause kidney stones or problems, nausea or constipation, or fatigue and weakness.

Blood tests show a high level of calcium and alkaline phosphatase (a bone chemical). Phosphorus may be low. The level of parathyroid hormone is elevated.

X-rays may show thin bones, fractures, bowing, and cysts. The cysts may be filled with clear fluid or filled with material ("brown tumors"). The skull may look like "ground glass" or "salt and pepper." The outer part of bones may be eroded; the most sensitive area to check is the fingers. Teeth X-rays may also be abnormal.

The main treatment for hyperparathyroidism is surgery to remove the abnormal parathyroid gland(s).

Newer techniques use radioactive tracers and rapid parathyroid hormone blood tests to make the surgery quicker and easier. If surgery is not possible, drugs can sometimes be used to lower calcium levels.

The bone problems of osteitis fibrosa cystica are usually reversible with surgery, except for the fluid-filled cysts.

The complications of osteitis fibrosa cystica include bone fractures, pain, and deformities. There may be other problems stemming from the hyperparathyroidism itself, such as kidney stones and kidney failure.

A physician should be called if you notice bone pain, tenderness, or if you have a fracture or any of the symptoms of hyperparathyroidism.

Today, most people have blood tests from time to time. Therefore, high calcium levels are usually found before any severe damage is done.

A bone density test (X-ray measure of bone strength) can be done. People with hyperparathyroidism are more likely to have just osteopenia (thin bones) or osteoporosis (very thin bones) than to have full-blown osteitis fibrosa cystica.

Most patients with hyperparathyroidism have no symptoms, and many can be followed with blood tests and bone measurements. Others are advised to have surgery, to prevent further problems.