Hyperparathyroidism

Hyperparathyroidism is when your parathyroid glands create high amounts of parathyroid hormone in the bloodstream. These glands, located behind the thyroid at the bottom of your neck, are about the size of a grain of rice.

The parathyroid hormone produced by the thyroid glands helps maintain the right balance of calcium in the bloodstream and in tissues that depend on calcium for proper functioning. This is especially important for nerve and muscle function, as well as bone health.

There are two types of hyperparathyroidism. In primary hyperparathyroidism, an enlargement of one or more of the parathyroid glands causes overproduction of parathyroid hormone. This causes high calcium levels in the blood, which can cause a variety of health problems. Surgery is the most common treatment for primary hyperparathyroidism.

Secondary hyperparathyroidism occurs due to another disease that first causes low calcium levels in the body. Over time, increased parathyroid hormone levels occur as the body fights to keep the calcium level up in the standard range. This is common in kidney disease and after certain intestinal surgeries or diseases.

Primary hyperparathyroidism is often diagnosed before signs or symptoms of the disorder occur. This is usually because an elevated level of calcium is found on routine blood tests. When symptoms do occur, they're the result of damage or dysfunction in other organs or tissues. This damage or dysfunction is due to high calcium levels in the blood and urine or too little calcium in bones.

Symptoms may be so mild and nonspecific that they don't seem related to parathyroid function, or they may be severe. The range of signs and symptoms include:

• Weak bones that break easily (osteoporosis)
• Kidney stones
• Excessive urination
• Stomach (abdominal) pain
• Tiring easily or weakness
• Depression or forgetfulness
• Bone and joint pain
• Frequent complaints of illness with no clear cause
• Nausea, vomiting or loss of appetite

See your health care provider if you have any signs or symptoms of hyperparathyroidism. These symptoms could be caused by many disorders, including some with serious complications. It's important to get a prompt, accurate diagnosis and the right treatment.

Hyperparathyroidism is caused by factors that increase the production of parathyroid hormone.

The parathyroid glands keep proper levels of both calcium and phosphorus in your body by turning the release of parathyroid hormone off or on. This is similar to how a thermostat controls a heating system to maintain a constant air temperature. Vitamin D also is involved in controlling the amount of calcium in your blood.

Normally, this balancing act works well.

• When calcium levels in your blood fall too low, your parathyroid glands release enough parathyroid hormone to restore the balance. This hormone raises calcium levels by releasing calcium from your bones, increasing the amount of calcium absorbed from your small intestine and decreasing the amount of calcium lost in urine.
• When blood-calcium levels are too high, the parathyroid glands produce less parathyroid hormone.

Calcium is best known for its role in keeping your teeth and bones healthy. But calcium also aids in the transmission of signals in nerve cells. And it's involved in muscle contraction. Phosphorus, another mineral, works along with calcium in these areas.

Sometimes one or more of the parathyroid glands produce high amounts of parathyroid hormone. These high hormone levels can be the body responding appropriately to keep the calcium in the standard range, or they may be inappropriately elevating the calcium in the blood. Which one depends on the underlying problem.

Hyperparathyroidism may occur because of primary hyperparathyroidism or secondary hyperparathyroidism.

Primary hyperparathyroidism

Primary hyperparathyroidism occurs because of a problem with one or more of the four parathyroid glands:

• A noncancerous growth (adenoma) on a gland is the most common cause.
• Enlargement (hyperplasia) of two or more parathyroid glands accounts for most other cases.
• A cancerous tumor is a very rare cause of primary hyperparathyroidism.

One or more of the parathyroid glands produces high amounts of parathyroid hormone. This leads to high calcium levels and low phosphorus levels in your blood. Primary hyperparathyroidism usually occurs randomly. But some people inherit a gene that causes the disorder.

Secondary hyperparathyroidism

Secondary hyperparathyroidism is the result of another condition that lowers the blood calcium, which then affects the gland's function. This causes your parathyroid glands to overwork and produce high amounts of parathyroid hormone to maintain or restore the calcium level to the standard range. Factors that may result in secondary hyperparathyroidism include:

• Severe calcium deficiency. Your body may not get enough calcium from your diet, often because your digestive system doesn't absorb the calcium from food. This is common after intestinal surgery, including weight loss surgery.

• Severe vitamin D deficiency. Vitamin D helps maintain appropriate calcium levels in the blood. It also helps your digestive system absorb calcium from your food.

  Your body produces vitamin D when your skin is exposed to sunlight. You also get some vitamin D in food. If you don't get enough vitamin D, then calcium levels may drop.

• Chronic kidney failure. Your kidneys convert vitamin D into a form that your body can use. If your kidneys work poorly, usable vitamin D may decrease and calcium levels drop. This causes parathyroid hormone levels to go up. Chronic kidney failure is the most common cause of secondary hyperparathyroidism.

  In some people with long-term secondary hyperparathyroidism, usually from end-stage kidney disease, the parathyroid glands enlarge. They begin to release parathyroid hormone on their own. The hormone level doesn't go down with medical treatment and the blood calcium becomes too high. This is called tertiary hyperparathyroidism, and people with this condition may require surgery to remove parathyroid tissue.

You may be at an increased risk of primary hyperparathyroidism if you:

• Are a woman who has gone through menopause
• Have had prolonged, severe calcium or vitamin D deficiency
• Have a rare, inherited disorder, such as multiple endocrine neoplasia, type 1, which usually affects multiple glands
• Have had radiation treatment for cancer that has exposed your neck to radiation
• Have taken lithium, a drug most often used to treat bipolar disorder

Complications of hyperparathyroidism are mainly related to the long-term effect of too little calcium in your bones and too much calcium in your bloodstream. Common complications include:

• Osteoporosis. The loss of calcium from bones often results in weak, brittle bones that break easily (osteoporosis).
• Kidney stones. Too much calcium in your blood may lead to too much calcium in your urine. This can cause small, hard deposits of calcium and other substances to form in your kidneys (kidney stone). A kidney stone usually causes major pain as it passes from the kidneys through the urinary tract.
• Cardiovascular disease. Although the exact cause-and-effect link is unclear, high calcium levels are associated with heart and blood vessel (cardiovascular) conditions, such as high blood pressure and certain types of heart disease.
• Neonatal hypoparathyroidism. Severe, untreated hyperparathyroidism in pregnant women may cause dangerously low levels of calcium in newborns. Primary hyperparathyroidism is not common in women of childbearing age.