Parathyroid hyperplasia is the enlargement of all four parathyroid glands. The parathyroid glands are located in the neck and control the body's break down of calcium. Parathyroid hyperplasia leads to high levels of calcium in the blood (hypercalcemia).

Parathyroid hyperplasia causes about 15% of cases of hyperparathyroidism, which leads to elevated levels of calcium in the blood (hypercalcemia).

Parathyroid hyperplasia may occur sporadically (without a family history) or as part of three familial (inherited) syndromes: multiple endocrine neoplasia 1 (MEN 1) and MEN 2A and isolated familial hyperparathyroidism.

In the familial syndromes, a mutated gene is inherited in an autosomal dominant fashion (you only need to get the gene from one parent to develop the condition).

In MEN 1, the problems in the parathyroids are associated with other tumors in the pituitary and the pancreas. In MEN 2A, the overactivity of the parathyroids is associated with tumors in the adrenal gland or thyroid.

The genetic basis of isolated familial parathyroidism is not yet clear.

Symptoms may include:

• Lethargy
• Nausea
• Constipation
• Myalgias (muscle pains)
• Kidney stones
• Bone fractures

The patient may have signs of fractures and renal colic.

Tests may show:

• Higher-than-normal serum calcium
• Low serum phosphorus
• Higher-than-normal PTH
• Higher-than-normal serum chloride
• Low serum bicarbonate
• Higher-than-normal 24-hour urine calcium
• Low bone mineral density

Surgery is the preferred treatment. Usually 3 1/2 glands are removed. The remaining tissue may be implanted in the forearm to regulate calcium levels but allow easy surgical access if hypercalcemia recurs.

The success rate for surgery for parathyroid hyperplasia is lower than that for parathyroid adenoma. Persistent or recurrent hypercalcemia occurs about 20% of the time.

Advanced complications of hyperparathyroidism associated with parathyroid hyperplasia include nephrocalcinosis and osteitis fibrosa cystica.

Patients may also have complications from the other endocrine tumors that are part of the multiple endocrine neoplasia syndromes:

• MEN 1 -- includes pancreatic and pituitary tumors, adrenal adenomas and lipomas
• MEN 2A -- includes medullary carcinoma of the thyroid and pheochromocytoma

Call your health care provider if you have any symptoms of hypercalcemia, or there is a family history of any of the MEN syndromes

Patients with a family history of the MEN syndromes may be genetically screened for presence of the defective gene and then screened regularly with standard diagnostic methods for endocrine problems if this test is positive.