Definition of Parathyroid hyperplasia:

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).

Causes, incidence, and risk factors:

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.