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 Hyperparathyroidism Hyperparathyroidism occurs when overactive parathyroid glands cause levels of parathyroid hormone (PTH) in the blood to become elevated. An elevated PTH level then leads to a high level of calcium... read more , lead to an increase in the blood level of calcium ( hypercalcemia Hypercalcemia (High Level of Calcium in the Blood) In hypercalcemia, the level of calcium in blood is too high. A high calcium level may result from a problem with the parathyroid glands, as well as from diet, cancer, or disorders affecting... read more ). 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 Overview of Parathyroid Function (See also Overview of the Thyroid Gland; Hypercalcemia; and Hypocalcemia.) The thyroid is a small gland, measuring about 2 inches (5 centimeters) across, that lies just under the skin below... read more .)
The Parathyroid Glands
Parathyroid adenomas are benign tumors that secrete excessive amounts of PTH, leading to hyperparathyroidism Hyperparathyroidism Hyperparathyroidism occurs when overactive parathyroid glands cause levels of parathyroid hormone (PTH) in the blood to become elevated. An elevated PTH level then leads to a high level of calcium... read more . In addition to hypercalcemia, hyperparathyroidism causes
Hypophosphatemia Hypophosphatemia (Low Level of Phosphate in the Blood) In hypophosphatemia, the level of phosphate in blood is too low. (See also Overview of Electrolytes and Overview of Phosphate's Role in the Body.) Phosphate is one of the body's electrolytes... read more (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 Osteoporosis Osteoporosis is a condition in which a decrease in the density of bones weakens the bones, making breaks (fractures) likely. Aging, estrogen deficiency, low vitamin D or calcium intake, and... read more
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 Multiple Endocrine Neoplasia Syndromes (MEN) Multiple endocrine neoplasia syndromes are rare, inherited disorders in which several endocrine glands develop noncancerous (benign) or cancerous (malignant) tumors or grow excessively without... read more (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 Stones in the Urinary Tract Stones (calculi) are hard masses that form in the urinary tract and may cause pain, bleeding, or an infection or block of the flow of urine. Tiny stones may cause no symptoms, but larger stones... read more .
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 calcium levels
Measurement of 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 ultrasonography, 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).
Occasionally, doctors give drugs such as cinacalcet or etelcalcetide to decrease secretion of PTH.
Parathyroid cancers are rare.
Risk factors for parathyroid cancer include
Radiation therapy to the neck
Family history of parathyroid tumors
The hyperparathyroidism and hypercalcemia due to parathyroid cancer are more severe than those due to parathyroid adenomas.
Symptoms are due to hypercalcemia Hypercalcemia (High Level of Calcium in the Blood) In hypercalcemia, the level of calcium in blood is too high. A high calcium level may result from a problem with the parathyroid glands, as well as from diet, cancer, or disorders affecting... read more 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.
Parathyroid cancers are usually removed surgically. Sometimes radiation therapy Radiation Therapy for Cancer Radiation is a form of intense energy generated by a radioactive substance, such as cobalt, or by specialized equipment, such as an atomic particle (linear) accelerator. Radiation preferentially... read more and/or chemotherapy Chemotherapy Chemotherapy involves the use of drugs to destroy cancer cells. Although an ideal drug would destroy cancer cells without harming normal cells, most drugs are not that selective. Instead, drugs... read more 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, hyperparathyroid cancers metastasize (spread to other areas of the body).