The parathyroid glands are located near the thyroid gland. Their exact location, and even the total number of glands, is quite variable. These glands secrete parathyroid hormone (PTH), which regulates calcium levels in the blood and tissues through its effects on bones, the kidneys, and the intestine.
Most parathyroid tumors are benign (not cancerous). Parathyroid tumors secrete parathyroid hormone (PTH) over and above what is normally secreted by the parathyroid glands.
Elevated PTH levels, known as hyperparathyroidism, lead to an increase in the blood level of calcium (hypercalcemia). At first, people with hypercalcemia have weakness and fatigue, constipation, loss of appetite, poor concentration, memory loss, and increased urination. If severe, hypercalcemia leads to confusion and eventually coma. If not recognized and treated, the disorder can be life threatening.
(See also Overview of Parathyroid Function and the figure The Parathyroid Glands.)
Parathyroid Adenoma
Parathyroid adenomas are benign tumors that secrete excessive amounts of PTH, leading to hyperparathyroidism. In addition to hypercalcemia, hyperparathyroidism causes
Hypophosphatemia (low level of phosphate in the blood)
Release of the calcium and phosphate stored in the bones into the blood (bone resorption), which leads to osteoporosis
Parathyroid adenomas usually occur as isolated solitary tumors, and they are more common among older women. However, multiple parathyroid adenomas may occur in hereditary syndromes in people with multiple endocrine neoplasia (MEN). MEN syndromes are rare inherited disorders in which several endocrine glands (those that release hormones directly into the bloodstream) develop benign (noncancerous) or malignant (cancerous) tumors. Alternatively, the endocrine glands may simply become enlarged without forming tumors.
Most parathyroid adenomas do not cause symptoms and are identified when blood tests done for another reason reveal high calcium levels. If symptoms occur, they are usually due to hypercalcemia or kidney stones.
Doctors diagnose hyperparathyroidism based on elevated PTH levels in people with hypercalcemia. If the doctor finds elevated levels of PTH, further tests are needed, including
Measurement of blood and urine calcium levels
Measurement of blood and urine phosphorus levels
Imaging studies (to evaluate bone density and determine the presence of kidney stones)
Doctors sometimes use various imaging studies, such as high-resolution computed tomography (CT) with or without biopsy, magnetic resonance imaging (MRI), high-resolution ultrasound, or angiography to identify the adenoma before surgery.
Treatment is usually surgical removal of the affected parathyroid gland. For people with only mildly elevated calcium levels who do not have symptoms or complications, doctors may instead monitor them regularly (called active surveillance).
Parathyroid Cancer
Parathyroid cancers are rare.
Risk factors for parathyroid cancer include
Radiation therapy to the neck
Family history of parathyroid tumors
Multiple endocrine neoplasia (MEN) syndrome
The hyperparathyroidism and hypercalcemia due to parathyroid cancer are more severe than those due to parathyroid adenomas.
Symptoms are due to hypercalcemia and include weakness and fatigue, constipation, loss of appetite, poor concentration, memory loss, confusion, and increased urination.
Doctors diagnose parathyroid cancers with blood tests to detect elevated levels of PTH and with imaging tests to locate tumors. Because some risk factors for parathyroid cancer tend to run in families, doctors sometimes recommend genetic screening of family members.
Parathyroid cancers are usually removed surgically. Sometimes radiation therapy and/or chemotherapy are also needed.
Parathyroid cancers usually grow slowly. If the surgeon is able to cleanly remove the entire gland, long-term survival without recurrence is likely. Any cancer that does recur usually grows slowly and spreads locally in the neck. Occasionally, parathyroid cancers metastasize (spread to other areas of the body).
