Osteitis fibrosa cystica is serious a medical condition that results from hyperparathyroidism.

If you have hyperparathyroidism, it means at least one of your parathyroid glands is making too much parathyroid hormone (PTH). The hormone is essential for bone health, but too much can weaken your bones and cause them to become deformed.

Osteitis fibrosa cystica is a rare complication of hyperparathyroidism, affecting less than 5 percent of people with the hormone disorder.

You have four tiny parathyroid glands in your neck. They produce PTH, which helps your body maintain healthy levels of calcium and phosphorous in your bloodstream and in tissue throughout your body. When calcium levels get too high, the parathyroid glands make less PTH. If calcium levels drop, the glands increase their PTH production.

Bones can respond to PTH differently. In some cases, PTH isn’t enough to overcome low calcium levels. Some bones may have weak areas with little or no calcium.

There appear to be two main causes of osteitis fibrosa cystica: primary hyperparathyroidism and secondary hyperparathyroidism. With primary hyperparathyroidism, there is a problem with the parathyroid glands. A cancerous or noncancerous growth on one of these glands may cause it to function abnormally. Other causes of primary hyperparathyroidism include hyperplasia or the enlargement of two more glands.

Secondary hyperparathyroidism occurs when you have some other health condition that reduces your calcium levels. As a result, the parathyroid glands work harder to try to boost your calcium. Two of the main triggers of low calcium are vitamin D deficiency and dietary calcium deficiency.

Vitamin D helps balance your calcium levels. If you don’t get enough vitamin D in your diet or you don’t get enough sun exposure (your body converts sunlight into vitamin D), your calcium levels can drop dramatically. Likewise, if you’re not eating enough food sources of calcium (spinach, dairy, soybeans, among others), low calcium levels could trigger an overproduction of PTH.

The most serious symptom of osteitis fibrosa cystica is an actual bone fracture. But before that happens, you may notice bone pain and tenderness, as well as these symptoms:

If your doctor suspects an imbalance of minerals, they’ll typically order a blood test. Your doctor can check for levels of calcium, phosphorous, PTH, and alkaline phosphatase, a bone chemical and a marker of bone health.

An X-ray can reveal bone fractures or areas of bone thinning. These images can also show if bones are bowing or becoming otherwise deformed. If you have hyperparathyroidism, you’re at greater risk of osteoporosis, a condition in which bones become more brittle. It’s usually related to hormonal changes brought on by menopause and aging.

If your osteitis fibrosa cystica is the result of an abnormal parathyroid gland, your best treatment option may be to have it surgically removed. This can often be done safely and effectively. The other parathyroid glands may be able to produce sufficient levels of PTH to compensate for the loss of one gland.

If surgery isn’t an option or you don’t want to have the gland removed, medications may be enough to treat your condition. Calcimimetics are drugs that mimic calcium in the blood. They help “trick” the parathyroid gland into producing less PTH. Bisphosphonates are also prescribed to people experiencing bone mass loss, but they are only meant for short-term use.

Hormone replacement therapy may also help the bones retain more calcium in women who are going through or have recently gone through menopause.

The earlier hyperparathyroidism is diagnosed and treated, the greater the chance of limiting the damage caused by osteitis fibrosa cystica. Taking medications to improve bone strength can be a great help. If you take other steps, such as doing weight-bearing exercises and boosting your calcium and vitamin D intake, you may be able to overcome the bone-relate complications associated with hyperparathyroidism.

If you feel your diet is lacking in vitamin D or calcium, talk with your doctor or a nutritionist about how to change your eating style. You should also discuss sun exposure with your doctor, especially if you live in a northern area where winter sunlight is at a minimum.

You can take an even more proactive step in managing your calcium levels by having routine blood work. A blood test that shows low calcium levels can prompt your doctor to recommend calcium and vitamin D supplements or to do further testing of your bone health.

You should also see your doctor as soon as you feel any pain or tenderness in your bones. You have options to manage your bone health and improve your calcium levels. If you’re proactive about these things, you can avoid fractures and other complications that can limit your mobility and your quality of life.