What is Parathyroid Disease?
Parathyroid disease refers to problems with the parathyroid glands. Almost everyone has four parathyroid glands, located in the neck near the thyroid. These glands exist to regulate blood calcium levels, so parathyroid disease is fundamentally a problem of calcium. The calcium in your blood is kept in a very tight range - your body doesn’t want it too low or too high. The parathyroids are what keep calcium in range. When the blood calcium level is low, your parathryoid glands become more active and release more parathyroid hormone (PTH), which increases blood calcium levels. If the blood calcium goes too high, the parathyroid glands essentially “shut down” and stop making so much PTH. This allows the blood calcium level to drop back to normal range. Your parathyroid glands are continuously monitoring calcium levels and adjusting their hormone release based on those levels.
The most common problem of the parathyroids is called primary hyperparathyroidism. In this condition, one or more parathyroid glands are diseased and overactive, producing too much parathyroid hormone (PTH). As the calcium rises, the diseased parathyroid does not turn off PTH production like it should, so it continues to produce PTH even as the calcium rises into the high range. Usually, primary hyperparathyroidism is caused by a benign parathyroid tumor called a parathyroid adenoma. Sometimes it is caused by parathyroid hyperplasia, which is an enlargement and overgrowth of all four parathyroid glands, and sometimes it is caused by multiple adenomas. The treatment for primary hyperparathyroidism is surgical removal of the diseased parathyroids (up to 3.5 glands in the case of hyperplasia, since you need to have some parathyroid in order to keep calcium levels from dropping too low). There are no medications that can cure primary hyperparathyroidism.
The other common form of parathyroid disease is called secondary hyperparathyroidism. Here, the parathyroids are overactive, but the problem did not start with the parathyroids. The problem started with chronically low calcium levels or issues with calcium absorption. Low calcium levels cause the parathyroids to release more and more PTH in an attempt to get the calcium up. The calcium might remain low for several reasons, including severe Vitamin D deficiency, history of gastric bypass or other intestinal surgery, chronic diarrhea, or renal failure. In secondary hyperparathyroidism, the parathyroid glands are doing what they are supposed to do - they are responding to low calcium by making more hormone. Unfortunately it is not working, so the parathyroid glands keep making more hormone and even start to bulk up. The treatment for this is usually not surgical. First-line treatment is aggressive supplementation with calcium and Vitamin D. When the calcium level stays in the normal range, the PTH may drop back to normal. Surgical intervention is necessary in some cases of secondary hyperparathyroidism, particularly if the glands have grown so much that they can no longer “turn off,” even when the calcium is back in normal range. In this case, a debulking (removing the largest 3 parathyroids and part of the fourth) can help.
Hypoparathyroidism (note that it is hypO, not hypER) is a rare condition characterized by abnormally low or absent parathyroid hormone (PTH). Most often this occurs as a complication of thyroid or parathyroid surgery, when all four parathyroid glands are injured or removed. Hypoparathyroidism can also occur in someone who has not had neck surgery, though this is very rare. To some extent, everyone who has parathyroid surgery can have a mild and temporary hypoparathyroidism in the days and weeks after surgery, but this resolves when the remaining parathyroids recover. Permanent hypoparathyroidism results in lifelong low calcium levels. It is treated with activated Vitamin D and calcium supplements. There is a daily injectable form of PTH that can help as well. The questions and answers on this site deal primarily with hypERparathyroidism, or overactive parathyroids, rather than hypoparathyroidism.