Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Parathyroid Cancer

What Is It?

Parathyroid cancer, also called parathyroid carcinoma, is a very rare cancer that develops in the parathyroid glands, two pairs of pea-sized glands located next to the thyroid in the front of the neck. The parathyroid glands produce parathyroid hormone (PTH), a chemical that enters the bloodstream and raises calcium levels in the blood. It does this by forcing the bones to release calcium, stimulating the intestines to absorb more calcium from food, and signaling the kidneys to withhold calcium from the urine. Normally, the parathyroid glands have a natural feedback mechanism that allows them to adjust their production of PTH to maintain blood calcium levels in the normal range.

When parathyroid cells become malignant (cancerous), they multiply out of control and typically form a firm, grayish-white tumor that can invade the nearby thyroid gland and neck muscles. As the cancerous cells grow, they usually produce too much PTH. In most cases, the end result is abnormally high levels of PTH in the blood (hyperparathyroidism) with abnormally high levels of calcium in the blood (hypercalcemia). The levels of PTH are so high that they force the bones to pour out critical amounts of calcium, which can cause bone pain and can lead to osteoporosis (thinning of the bones). The elevated PTH also forces the kidneys to retain large amounts of calcium, triggering the formation of kidney stones. Excessively high calcium levels also can cause kidney damage, dehydration and changes in neurological function including confusion. More often, an enlargement of the parathyroid gland may be due to a benign enlargement of the gland, called an adenoma.

Parathyroid cancer is so rare that even a major medical center may see no more than two dozen patients with the illness over a period of several decades. About 1 of every 2,000 people in the United States is diagnosed with hyperparathyroidism in any given year, but only 20 to 40 of these patients have parathyroid cancer. Parathyroid cancer occurs most commonly in adults between 45 and 51 years old, although cases have occurred in people as young as 19 and as old as 81. Because parathyroid cancer is so rare, researchers have not been able to determine whether there are any specific environmental or lifestyle factors that increase the risk of this illness. A few cases have shown an inherited tendency, with several generations of a single family affected.