Hyperparathyroidism is an excess of parathyroid hormone in the bloodstream due to overactivity of one or more of the body’s four parathyroid glands. These glands are about the size of a grain of rice and are located in your neck next to your thyroid gland.
The parathyroid glands produce parathyroid hormone, which helps maintain an appropriate balance of calcium in the bloodstream and in tissues that depend on calcium for proper functioning.
Two types of hyperparathyroidism exist:
In primary hyperparathyroidism, an enlargement of one or more of the parathyroid glands causes overproduction of the hormone, resulting in high levels of calcium in the blood (hypercalcemia), which can cause a variety of health problems. Surgery is the most common treatment for primary hyperparathyroidism.
Secondary hyperparathyroidism occurs as a result of another disease (typically kidney disease) that initially causes low levels of calcium in the body and over time, increased parathyroid hormone levels occur.
Hyperparathyroidism is often diagnosed before signs or symptoms of the disorder are apparent. When symptoms do occur, they’re the result of damage or dysfunction in other organs or tissues due to high calcium levels circulating in the blood and urine or too little calcium in bones.
Symptoms may be so mild and nonspecific that they don’t seem at all related to parathyroid function, or they may be severe. The range of signs and symptoms include:
- Fragile bones that easily fracture (osteoporosis)
- Kidney stones
- Excessive urination
- Abdominal pain
- Tiring easily or weakness
- Depression or forgetfulness
- Bone and joint pain
- Frequent complaints of illness with no apparent cause
- Nausea, vomiting or loss of appetite
Hyperparathyroidism is caused by factors that increase the production of parathyroid hormone.
The parathyroid glands maintain proper levels of both calcium and phosphorus in your body by turning the secretion of parathyroid hormone (PTH) off or on, much like a thermostat controls a heating system to maintain a constant air temperature. Vitamin D also is involved in regulating 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 secrete enough PTH to restore the balance. PTH raises calcium levels by releasing calcium from your bones and increasing the amount of calcium absorbed from your small intestine.
When blood-calcium levels are too high, the parathyroid glands produce less PTH. But sometimes one or more of these glands produce too much hormone, leading to abnormally high levels of calcium (hypercalcemia) and low levels of phosphorus in your blood.
The mineral calcium is best known for its role in keeping your teeth and bones healthy. But calcium has other functions. It aids in the transmission of signals in nerve cells, and it’s involved in muscle contraction. Phosphorus, another mineral, works in conjunction with calcium in these areas.
The disorder can generally be divided into two types based on the cause. Hyperparathyroidism may occur because of a problem with the parathyroid glands themselves (primary hyperparathyroidism) or because of another disease that affects the glands’ function (secondary hyperparathyroidism).
Primary hyperparathyroidism occurs because of some 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 (malignant) tumor is an extremely rare cause of primary hyperparathyroidism.
Primary hyperparathyroidism usually occurs randomly, but some people inherit a gene that causes the disorder.
Secondary hyperparathyroidism is the result of another condition that lowers calcium levels. Therefore, your parathyroid glands overwork to compensate for the loss of calcium. Factors that may contribute to 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 it.
- Severe vitamin D deficiency. Vitamin D helps maintain appropriate levels of calcium in the blood, and it helps your digestive system absorb calcium from your food.
- Your body produces vitamin D when your skin is exposed to sunlight, and you consume 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 function poorly, usable vitamin D may decline and calcium levels drop. Chronic kidney failure is the most common cause of secondary hyperparathyroidism.
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 primarily related to the long-term effect of too little calcium in your bones and too much calcium circulating in your bloodstream. Common complications include:
- Osteoporosis. The loss of calcium often results in weak, brittle bones that fracture easily (osteoporosis).
- Kidney stones. The excess of calcium in your blood may lead to excess calcium in your urine, which can cause small, hard deposits of calcium and other substances to form in your kidneys. A kidney stone usually causes significant pain as it passes through the urinary tract.
- Cardiovascular disease. Although the exact cause-and-effect link is unclear, high calcium levels are associated with cardiovascular conditions, such as high blood pressure (hypertension) and certain types of heart disease.
If the result of a blood test indicates you have elevated calcium in your blood, your doctor will likely repeat the test to confirm the results after you have not eaten for a period of time (fasted).
A number of conditions can raise calcium levels, but your doctor can make a diagnosis of hyperparathyroidism if blood tests show you also have elevated parathyroid hormone.
Additional diagnostic tests
After making a diagnosis of hyperparathyroidism, your doctor will likely order additional tests to rule out possible secondary causes, to identify possible complications and to judge the severity of the condition. These tests include:
- Bone mineral density test (bone densitometry). The most common test to measure bone mineral density is dual energy X-ray absorptiometry (DXA).This test uses special X-ray devices to measure how many grams of calcium and other bone minerals are packed into a segment of bone.
- Urine test. A 24-hour collection of urine can provide information on how well your kidneys function and how much calcium is excreted in your urine.This test may help in judging the severity of hyperparathyroidism or diagnosing a kidney disorder causing hyperparathyroidism. If a very low level of calcium in the urine is found, this may indicate a condition that doesn’t require treatment.
- Imaging tests of kidneys. Your doctor may order X-rays or other imaging tests of your abdomen to determine if you have kidney stones or other kidney abnormalities.
Imaging tests before surgery
If your doctor recommends surgery, he or she will likely use one of these imaging tests to locate the parathyroid gland or glands that are causing problems:
- Sestamibi parathyroid scan. Sestamibi is a radioactive compound that is absorbed by overactive parathyroid glands and can be detected by a scanner that detects radioactivity.The normal thyroid gland also absorbs sestamibi. To eliminate uptake in the thyroid obscuring the uptake in a parathyroid adenoma, radioactive iodine, which is only taken up by the thyroid, also is given and the thyroid image is digitally subtracted.Computerized tomography (CT) scanning may be combined with the sestamibi scan to improve detection of an abnormality.
- Ultrasound. Ultrasound uses sound waves to create images of your parathyroid glands and surrounding tissue.A small device held against your skin (transducer) emits high-pitched sound waves and records the sound wave echoes as they reflect off internal structures. A computer converts the echoes into images on a monitor.