The parathyroid glands are different than the thyroid gland, even though the names are similar. The four parathyroid glands are usually on the back of the thyroid gland, but they can be located around the jaw or neck.
In the United States, about 100,000 people develop hyperparathyroidism each year. Women outnumber men two to one, and risk increases with age. In women 60 years and older, two out of 1,000 will develop hyperparathyroidism each year.
When the parathyroid glands secrete too much hormone, blood calcium rises. This condition of excessive calcium in the blood, called hypercalcemia, is what usually signals the doctor that something may be wrong with the parathyroid glands. In 85 percent of people with primary hyperparathyroidism, a benign tumor called an adenoma has formed on one of the parathyroid glands, causing it to become overactive. Benign tumors are noncancerous. In most other cases, the excess hormone comes from two or more enlarged parathyroid glands, a condition called hyperplasia. Very rarely, hyperparathyroidism is caused by cancer of a parathyroid gland.
This excess PTH triggers the release of too much calcium into the bloodstream. The bones may lose calcium, and too much calcium may be absorbed from food. The levels of calcium may increase in the urine, causing kidney stones. PTH also lowers blood phosphorus levels by increasing excretion of phosphorus in the urine.
Calcium is essential for good health. It plays an important role in bone and tooth development and in maintaining bone strength.
Calcium is also important in nerve transmission and muscle contraction. Phosphorus is found in all bodily tissue. It is a main part of every cell with many roles in each. Combined with calcium, phosphorus gives strength and rigidity to your bones and teeth.
In most cases doctors don't know the cause of the condition. The vast majority of cases occur in people with no family history of the disorder. Only about five percent of cases can be linked to an inherited problem. Familial multiple endocrine neoplasia type 1 is a rare, inherited syndrome that affect the parathyroids, as well as the pancreas and the pituitary gland. Another rare genetic disorder, familial hypocalciuric hypercalcemia, is sometimes confused with typical hyperparathyroidism. Each accounts for about 2 percent of primary hyperparathyroidism cases. A childhood history of radiation treatments for acne or other condition in the head and neck area (common in the 1940s to 1950s) can also increase the risk of hyperparathyroidism.
A person with hyperparathyroidism may have severe symptoms, subtle ones, or none at all. More than 99 percent of the time, the parathyroid glands exhibit a benign enlargement, usually of only one gland, but sometimes more than one will be involved. Increasingly, routine blood tests that screen for a wide range of conditions, including high calcium levels, are alerting doctors to people who have mild forms of the disorder even though they are symptom-free.
When symptoms do appear, they are often mild and nonspecific, such as a feeling of weakness and fatigue, depression, or aches and pains. With more severe disease, a person may have a loss of appetite, nausea, vomiting, constipation, confusion or impaired thinking and memory, and increased thirst and urination. Patients may have thinning of the bones without symptoms, but with risk of fractures. Increased calcium and phosphorus excretion in the urine may cause kidney stones.
Hyperparathyroidism is diagnosed when tests show that blood levels of calcium and parathyroid hormone are too high. Other diseases can cause high blood calcium levels, but only in hyperparathyroidism is the elevated calcium the result of too much parathyroid hormone. A blood test that accurately measures the amount of parathyroid hormone has simplified the diagnosis of hyperparathyroidism.
Once the diagnosis is established, other tests may be done to assess complications. Because high PTH levels can cause bones to weaken from calcium loss, a measurement of bone density can help assess bone loss and the risk of fractures. Abdominal images may reveal the presence of kidney stones and a 24-hour urine collection may provide information on kidney damage, the risk of stone formation, and the risk of familial hypocalciuric hypercalcemia.
Although not all patients require surgery, the definitive therapy for treating this disorder is surgical removal of the parathyroid after it has been localized through nuclear medicine scanning and an ultrasound examination of the neck. Center surgeons are skilled at removing these glands with small incisions. They have the ability to measure parathyroid hormone concentrations in the operating room to help make sure that the levels drop after removal of the parathyroid gland, indicating that the abnormal gland was identified and appropriately treated. There are clinical trials currently examining medical therapy for hyperparathyroidism for those individuals who wish to avoid surgery or are too ill to undergo surgery.
When calcium levels become too high, removal of one or more of the parathyroid glands may be necessary (parathyroidectomy). A high resolution ultrasound or other nuclear medicine scan may be necessary to help the surgeon identify the precise location of the overactive gland(s). To preserve gland function, any remaining gland tissue can be transplanted to another site in the neck, or in the arm.
The generally recognized indications for referring a patient for surgical removal of the abnormal parathyroid include:
- Serum calcium that is persistently over 1 mg/dl of the upper limit normal for the laboratory
- Presence of kidney stones, osteoporosis at any site, peptic ulcer disease, pancreatitis, or kidney failure
- A 24-hour urine calcium that is above the upper limit of normal
- Age under 50 years
An experimental trial is being performed at Cedars-Sinai that involves giving a calcium sensing receptor blocker (SENSIPAR, Cinacalcet) to patients with primary hyperparathyroidism. This results in a lowering of the serum calcium and may improve symptoms and bone density.