The parathyroid glands are four small glands behind the thyroid gland. They usually are about the size of a kernel of corn. Usually, one parathyroid gland is located near each corner of the thyroid. Some people are missing a parathyroid gland or have an extra one. The parathyroid glands may be misplaced in other glands but still work normally.
Parathyroid glands make parathyroid hormone (PTH), which controls the levels of calcium and phosphorous in the blood. PTH also helps the body make vitamin D and helps prevent loss of too much calcium in the urine.
Parathyroid Disease Types
Hyperparathyroidism means the parathyroid makes too much PTH. Usually this is caused by an adenoma, which is a benign tumor on the parathyroid. Too much PTH may cause too much calcium in the blood, which is called hypercalcemia. This can cause serious problems, including osteoporosis (weakening of the bones) and kidney stones.
Cancer of the parathyroid glands is extremely rare. Sometimes parathyroid cancer causes hyperparathyroidism (HPT), which means the body makes too much PTH. However, less than 1% of people with HPT have parathyroid cancer. Men and women have the same risk for parathyroid disease, which usually strikes people in their 50s.
Although parathyroid cancer progresses slowly, it often comes back after treatment. The cancer returns at the original site in 36% to 80% of patients, anywhere from one month to 19 years after it was first treated. The average time before return is about two and a half years. Controlling the level of calcium in the blood can help people have longer disease-free periods between recurrences.
Hypoparathyroidism means the body does not make enough PTH and the calcium level in the blood is too low. Hypoparathyroidism usually is caused by neck surgery or damage to the parathyroid glands.
Parathyroid Disease Risk Factors
Anything that increases your chance of getting parathyroid disease is a risk factor.
Having certain inherited disorders can increase your risk of developing parathyroid cancer. These include:
- Familial isolated hyperparathyroidism (FIHP)
- Multiple endocrine neoplasia type 1 (MEN1)
Some cases of parathyroid disease can be passed down from one generation to the next. Genetic counseling may be right for you. Learn more about the risk to you and your family on our genetic testing page.