Part of the endocrine system of the body, the parathyroid glands comprise four pea-sized nodules located on or near the back of the thyroid gland in the throat. They primarily control the levels of calcium and phosphorus stored in the bones and circulated in the blood. To do that, they release a hormone called parathyroid hormone (PTH). Disorders occur either when the glands become either overactive or underactive.
When one or more of the glands become overactive, they release too much PTH. This signals the bones to release calcium into the blood, where it is excreted in the urine. The loss of calcium from the bones results in osteoporosis (weak bones). Hyperthyroidism is usually caused by a noncancerous tumor, called an adenoma, forming in one of the parathyroid glands.
Symptoms — usually caused by the high calcium levels — may include muscle weakness, fatigue, depression, and painful bones and joints. In worse cases, there may be a loss of appetite, nausea, vomiting, constipation, confusion, and increased thirst and urination. Surgical treatment to remove the affected gland is routine and highly effective.
When the parathyroid is underactive — a rarer condition — the level of PTH produced is too low for normal function. It leads to low levels of calcium and high levels of phosphorus, which can lead to problems in the bones, muscles, skin, and nerve endings.
It is most commonly caused by some injury to the parathyroid gland, perhaps from neck surgery. It is also even more rarely caused by a congenital disorder called autoimmune polyglandular failure type 1.
Treatment — usually through dietary changes and supplements — is intended to restore the balance of calcium, magnesium, and phosphorus levels in the blood and urine.