What is Hyperparathyroidism?

Hyperparathyroidism is a condition in which the parathyroid gland or glands produce an overabundance of parathyroid hormone (PTH), causing chemical imbalances in the body, frequently resulting in elevated serum calcium, or hypercalcemia.

Symptoms and Types

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.

Diagnosis and Tests

Elevated serum calcium and PTH noted on blood chemistry suggest the diagnosis of primary hyperparathyroidism. Nuclear medicine scintigraphy of the parathyroid, also known as a Sestamibi scan, can be used to localize the adenoma to the right or left side of the neck. This makes surgical removal of the abnormal gland, called parathyroidectomy, easier. Ultrasound may be used to further localize the adenoma. Secondary hyperparathyroidism is typically diagnosed by elevated PTH and phosphate in the typical clinical setting of chronic renal failure.