What is PTH?

PTH stands for parathyroid hormone. It's job is to regulate calcium in the body to a very narrow range. If the calcium level is low, normal parathyroid glands will produce more hormone (PTH) to compensate. If the calcium level is high, the normal parathyroid glands will produce less PTH. 

What causes overproduction of PTH (hyperparathyroidism)?

The most common cause for inappropriately high levels of PTH is a single gland that has lost it's normal controls. The glands, called adenomas, grow larger than the normal sized gland and loose the feedback mechanism that's supposed to regulate calcium in a narrow range. The larger these tumors (abnormal parathyroid glands) grow, the higher the PTH becomes. Higher PTH results in high calcium and all kinds of symptoms. More than 90% of the time, just one of the four parathyroids have become enlarged. A short operation to remove this abnormal gland (adenoma) restores normal calcium levels and relieves symptoms. 

In less than 10% of cases, there is overgrowth of all four of the parathyroid glands. This is called hyperplasia and is far more difficult to manage. There are two basic strategies to tackle this problem. One, is to remove three glands and about half of the fourth gland. The body needs only about one half of one normal sized parathyroid gland to have normal function. The second approach is to remove all four of the parathyroid glands and reimplant a portion of parathyroid tissue into a muscle of the neck or arm. This approach allows any subsequent intervention to focus on the area of reimplantation, away from the original location next to the delicate voice box nerves.