Hypoparathyroidism

Too Little Parathyroid Hormone Production

Hypoparathyroidism is the combination of symptoms due to inadequate parathyroid hormone production. This is a very rare condition and most commonly occurs because of damage to or removal of parathyroid glands at the time of parathyroid or thyroid surgery, but hypoparathyroidism may also be caused by other clinical conditions. There are normally four parathyroid glands that make parathyroid hormone which are located behind and next to the thyroid.

Hypoparathyroidism is the state of decreased secretion or activity of parathyroid hormone (PTH). A patient afflicted with this condition simply has too little (or a complete absence of) parathyroid tissue; therefore, inadequate PTH is produced. This leads to decreased blood levels of calcium (hypocalcemia) and increased levels of blood phosphorus (hyperphosphatemia). Symptoms can range from quite mild (tingling in the hands, fingers, and around the mouth) to more severe forms of muscle cramps leading to severe spasms of the hands or feet. The most severe symptoms are tetany (severe muscle cramping of the entire body), convulsions (this is very rare) or even death.
Parathyroid gland insufficiency is quite rare, but it can occur in several situations. The most common cause of hypoparathyroidism is the loss of active parathyroid tissue following thyroid or parathyroid surgery. Other rare causes are; a defect present at birth (congenital) where a person is born without parathyroid glands, magnesium deficiency or autoimmune destruction in polyglandular endocrine deficiency syndrome. Occasionally, the specific cause of hypoparathyroidism cannot be determined, which is called idiopathic.

Post-surgical Hypoparathyroidism

The first (and by far most common) cause of inadequate parathyroid hormone production is the removal of parathyroid glands during surgery. The operations that are typically associated with the problem are operations designed to remove parathyroid glands for hyperparathyroidism. The goal of this operation is to remove those parathyroid glands that are overproducing PTH. But occasionally, too much parathyroid tissue is removed.

Thyroid surgery is an unusual cause of hypoparathyroidism. Thyroid operations are performed for a number of reasons, but because of the close relationship that the thyroid and the parathyroid have to one another (including sharing the same blood supply), the parathyroid glands can be injured or removed. In most patients, the inadequate secretion of PTH is transient following surgery on the thyroid or parathyroid glands, so this diagnosis cannot be made immediately following surgery and may take several months to be sure whether or not the hypoparathyroidism is transient or permanent.

Congenital Hypoparathyroidism

Patients in this category are born without parathyroid glands. Most patients with congenital hypoparathyroidism have no family history of the disease. Those who do may have any one of a number of congenital causes. The inherited forms tend to arise from abnormal genes: 1) abnormal forms of PTH, which make it inactive, 2) defects in the receptor which prevent normal conduction of cells signals from the PTH receptor to the cell, or 3) defects in normal gland development before birth.

Hypoparathyroidism with onset during the first few months of life can be permanent or temporary. The cause is usually manifested by 24 months of age. Finally, mothers who have overactive parathyroid glands may have high calcium levels. The excess ionized calcium can enter the baby and suppress the baby’s parathyroid function. If suppression of the gland is not released quickly enough after birth, low calcium levels can be a temporary problem for the baby. This will not result in permanent parathyroid gland dysfunction in the child.

Hypomagnesemia

The element magnesium is closely related to calcium in the body. When magnesium levels are too low, calcium levels may also fall. It appears that magnesium is important for parathyroid cells to make PTH normally. Once recognized, this is usually very easy to fix by giving extra magnesium. Chronic alcoholism is a frequent cause of low calcium and magnesium levels.

Autoimmune Hypoparathyroidism

The acquired form of this disease typically arises because the immune system has developed antibodies against parathyroid cells (autoimmune disease) in an attempt to reject what it sees as a foreign tissue. This disease can affect the parathyroid glands in isolation or can be part of a syndrome that involves other endocrine glands.

Treatment of Hypoparathyroidism

Vitamin D formulations and calcium supplements are the primary treatments for hypoparathyroidism, regardless of the cause. The only exception is when the inactivity of PTH is due to hypomagnesemia, which is readily treated with magnesium replacement therapy. In permanent hypoparathyroidism, it is important to monitor the vitamin D levels and levels of calcium in the urine to prevent damage to the kidneys and other organs in the body. This monitoring is lifelong and is necessary every 6 -12 months. There have been medical advances with new preparations of PTH therapies available by injection but are reserved for the most severe cases.