There are generally four parathyroid glands, each about the size of a lentil bean (4mm), that are attached to the posterior aspect of the two lobes of the thyroid gland. There are two parathyroid glands in each side of the neck, each with its own individual blood supply. PTH is secreted from the glandular tissue and deposited into the blood stream, through which it travels to various parts of the body where it has its effects.
Normal PTH function: PTH is responsible for mobilizing calcium from bone, where it is stored, into the blood stream, where it can be used for normal cellular activity throughout the body. A feedback mechanism between the blood stream and the parathyroid glands maintains a serum calcium concentration within the narrow range necessary for normal bodily function.
Excessive PTH Function: Excessive secretion of PTH can lead to hypercalcemia and other chemical imbalances. Hypercalcemia can cause a number of symptoms and medical conditions, including mental confusion or psychiatric disturbances, kidney stones, pancreatitis, bone and joint pain, and abdominal pain.
Hypercalcemia can be either primary or secondary. Primary hypercalcemia is the most common, and results from the spontaneous enlargement and excessive secretion of a single parathyroid gland. This type of enlargement is known as a parathyroid adenoma, a benign tumor of the parathyroid gland. Occasionally, multiple parathyroid adenomas can be present. Secondary hyperparathyroidism is usually seen in patients with renal failure, who are receiving dialysis. This leads to diffuse enlargement of all four parathyroid glands resulting in hypersecretion of PTH. These patients do not have an adenoma, only a diffuse enlargement of otherwise normal appearing parathyroid tissue. Patients with secondary hyperparathyroidism may have problems with management of phosphate and aluminum.
What Treatment Options are Available?
Very early forms of hyperparathyroidism may have few or no associated symptoms. The process may not have persisted long enough to cause bone or kidney changes as the PTH level is has not yet been profoundly elevated. These cases are usually associated with smaller adenomas where the gland is too small to image. In some instances it may be appropriate to consider observation in this setting to allow the disease to progress until the gland is large enough be imaged. Typically, however, treatment is indicated once the problem is identified.
Parathyroidectomy is surgical removal of one or more parathyroid glands in order to treat hyperparathyroidism. When performed to treat primary hyperparathyroidism, only a single enlarged gland (parathyroid adenoma) is removed. When performed to treat secondary hyperparathyroidism, a subtotal parathyroidectomy is generally performed, in which at least three of the four glands are removed.
Parathyroidectomy is performed through an incision in the neck under general anesthetic. During excision of a parathyroid adenoma, the surgeon identifies the enlarged parathyroid gland on the posterior aspect of the thyroid gland and removes it. During subtotal parathyroidectomy, all four parathyroid glands are identified and three to three and a half glands are removed, leaving only a small remnant of parathyroid tissue in the body.