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 or removal of parathyroid glands at the time of parathyroid or thyroid surgery.   If this is the first parathyroid page you have read from our site, we strongly recommend that you read our introduction to the parathyroid gland first!  Remember, hyperparathyroidism is much more common than hypoparathyroidism.

Hypoparathyroidism is the state of decreased secretion or activity of parathyroid hormone (PTH).  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 all the way to tetany (severe muscle cramping of the entire body), and convulsions (this is very rare!).

Parathyroid gland insufficiency is quite rare, but it can occur in several well defined ways.  The most common cause of hypoparathyroidism is the loss of active parathyroid tissue following thyroid or parathyroid surgery.  More rare is a defect present at birth (congenital) where a person is born without parathyroid glands.  Occasionally, the specific cause of hypoparathyroidism cannot be determined.

Three Categories of Hypoparathyroidism (each discussed below)

[1]  Deficient Parathyroid Hormone Secretion.

[2]  Inability to make an active form of PTH.

[3]  Inability of the kidneys & bones to respond to PTH.

[1]  Deficient Parathyroid Hormone Secretion.

This type of hypoparathyroidism is the easiest to understand.  A patient afflicted with this condition simply has too little (or a complete absence of) parathyroid tissue therefore, inadequate PTH is produced.  There are two major causes of this problem:

   A)  Post Surgical.  The first (and by far the most common) mechanism by which inadequate parathyroid hormone is produced is due to the removal of parathyroid glands at the time of surgery.  The operations which are typically associated with this problem are operations designed to remove parathyroid glands for hyperparathyroidism.  The goal of this operation is to remove those parathyroid glands which are overproducing PTH, however, occasionally, (about 1%-2% of the time) too much parathyroid tissue is removed.  The second operation which is associated with postoperative hypoparathyroidism is total thyroidectomy.   This operation is performed for a number of reasons, but because of the close relationship that the thyroid and parathyroid have to one another (including sharing the same blood supply) the parathyroid glands can be injured or removed.  This is very rare and occurs in much less than 1% of thyroid operations.  In many 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.

HOWEVER... Hypoparathyroidism is a TERRIBLE complication of parathyroid or thyroid surgery. You MUST choose your surgeon wisely! If your surgeon does not perform parathyroid surgery AT LEAST once per week, then your risk of getting permanent hypoparathyroidism is about 5%. Hypoparathyroidism will ruin your life!  You MUST get an experienced parathyroid surgeon! We cannot over state this. Do not go to some "general surgeon" who does less than 50 parathyroid operations per year!

B) Idiopathic.   Deficient PTH secretion without a defined cause (e.g. surgical injury) is termed Idiopathic hypoparathyroidism.  This disease is rare and can be congenital or acquired later in life.

 Congenital.   Patients in this category are born without parathyroid tissues.  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 pattern of inheritance is as varied as the kinds of genetic abnormalities that cause the disease. The children in some families are at a 50% risk for disease (dominant gene defect) while others are at a risk of 25% or less (recessive gene defect). In some families only the boys suffer from disease. This sex-linked inheritance pattern indicates the presence of a genetic defect on the X chromosome. The inherited forms tend to arise from abnormal genes that either: 1) encode abnormal forms of PTH or its receptor, 2) prevent normal conduction of cell signals from the PTH receptor to the nucleus, or 3) prevent normal gland development before birth.

Hypoparathyroidism with onset during the first few months of life can be permanent or temporary. The cause is usually unknown and if spontaneous resolution occurs.  If it does not, it will usually become manifest 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 gland 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.

Acquired.   The acquired form of this disease typically arises because the immune system has developed antibodies against parathyroid tissues in an attempt to reject what is sees as a foreign tissue, much as it would a transplanted organ. This disease can affect the parathyroid glands in isolation or can be part of a syndrome that involves many organs. An antibody that binds to the calcium sensor in the parathyroid gland has been discovered in the blood of patients with autoimmune hypoparathyroidism. It has been proposed that such binding "tricks" the parathyroid gland into believing that the blood level of ionized calcium is high. Responding to this signal, the parathyroid stops making PTH.

C)   Hypomagnesemia.    The element magnesium is closely related to the action of 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.  Chronic alcoholism is a frequent cause of low calcium and magnesium levels.

[2] Secretion of Biologically Inactive Parathyroid Hormone.

This section is placed here for completion sake only.  There have only been a few cases of this syndrome ever reported, but one can see that if the PTH which is produced is actually a defective hormone, it would not have the same biologic strength as its normal counterpart.

[3] Resistance to Parathyroid Hormone  (pseudo-hypoparathyroidism).

This disease is also VERY RARE!  Like all patients with hypoparathyroidism, this disease is characterized by hypocalcemia (too low calcium levels), hyperphosphatemia (too high phosphorus levels), but they are distinguished by the fact that they produce PTH but their bones and kidneys do not respond to it.  Even if PTH is given to them in their veins, they do not respond to it.  Therefore, these rare individuals have plenty of PTH, but their organs do not behave appropriately to it (so they look to be hypoparathyroid but they are not...thus the name "pseudo-hypoparathyroid").

Treatment of Hypoparathyroidism

Vitamin D and calcium supplements are the primary treatments for this disease regardless of the cause.  The only exception is when the inactivity of PTH is due to hypomagnasemia which is readily treated with magnesium supplementation.  At this time, a replacement form of PTH is not available.

For more information on hypoparathyroidism go to Parathyroid.com. This web site is devoted completely to parathyroid disease and is very large--updated weekly.

CLICK HERE: www.parathyroid.com/hypoparathyroidism

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