Secondary hyperparathyroidism

Definition:

An increased activity of the parathyroid gland with excessive production of parathyroid hormone, in response to an abnormality outside the parathyroid gland that produces a condition of low calcium

Causes, incidence, and risk factors:

The parathyroid glands are at the front and base of the neck at the 4 corners of the thyroid gland. The glands produce a parathyroid hormone which regulates the calcium, phosphorus, and magnesium balance within the blood and normal bone mineralization.

With overproduction of the parathyroid hormone, the calcium level in the blood becomes elevated by removing calcium from the bones and increasing calcium absorption from the gastrointestinal (GI) tract. The kidneys attempt to compensate for the increased blood calcium level by secreting excess calcium in the urine, which can result in the formation of kidney stones.

In secondary hyperparathyroidism, an increase in the cells of the parathyroid glands, called hyperplasia, occurs. The causes of this disorder include rickets, vitamin D deficiency, or chronic renal failure. This is the most common cause of hyperparathyroidism in children.

The effects of increased parathyroid hormone are seen in the skeleton, stomach and intestines, kidneys, nervous system, and muscles. The severity of the condition can vary from mild to severe.

The incidence of mild secondary hyperparathyroidism is 1 out of 1000 people. The incidence of severe hyperparathyroidism is 1 out of 10,000 people.