Conditions: Hypoparathyroidism

What is hypoparathyroidism?

Hypoparathyroidism is an endocrine disorder characterized by insufficient production of parathyroid hormone (PTH) by the parathyroid glands. These four small glands located in the neck play a major role in regulating calcium and phosphorus levels in the blood. With low or absent PTH levels, blood calcium levels of calcium (hypocalcemia) occurs. Hypoparathyroidism causes hypocalcemia, but hypocalcemia may be caused by several other conditions besides hypoparathyroidism.

How do the parathyroid glands normally function?

The parathyroid glands play a crucial role in maintaining calcium levels in the body. These small, pea-sized glands, located in the visceral space of the neck (near the thyroid gland), produce and release parathyroid hormone (PTH). Normally, the parathyroid glands function by constantly monitoring the blood calcium levels. When the calcium levels drop, the parathyroid glands release PTH into the bloodstream. PTH stimulates the bones to release calcium into the blood, promotes calcium reabsorption by the kidneys, and enhances the absorption of calcium from the intestines. This concerted action of the parathyroid glands ensures that there is a sufficient supply of calcium in the blood to support proper nerve function, muscle contraction, blood clotting, and bone health. Conversely, when blood calcium levels are high, the parathyroid glands reduce the production and release of PTH, which helps prevent the excessive build-up of calcium in the blood.

what causes hypoparathyroidism?

Loss or dysfunction of all parathyroid glands is necessary to result in hypoparathyroidism. Although most individuals have four parathyroid glands, as little as one half of one gland can produce enough parathyroid hormone to regulate calcium normally. This redundancy is advantageous because surgery near the parathyroid glands (including surgery of the thyroid, parathyroid, nearby lymph nodes, upper trachea and upper esophagus) does risk unintended injury to or removal of one or more parathyroid glands. As the parathyroid glands are normally very small, are located in variable anatomic positions, can look like the surrounding tissues (thyroid, lymph node, or fat), have a very small blood supply, unintended loss of one or more parathyroid glands during nearby surgery may occur despite every effort to preserve them.

Despite the variable number and location of parathyroid glands, it is extremely uncommon for an individual not to have at least one left and at least one right gland at birth. And since as little as one half of one parathyroid gland is sufficient for normal parathyroid function, surgery on only one side of the visceral space of the neck has an essentially nonexistent risk of causing hypoparathyroidism. Surgery on both sides of the visceral space of the neck, whether in one operation or cumulatively over time, does incur risk of hypoparathyroidism.

Since parathyroids that are not physically removed may stop functioning only temporarily due to manipulation during surgery, post-operative hypoparathyroidism may be, and usually is, temporary. Permanent hypoparathyroidism can occur, however, with removal of all four parathyroid glands or permanent injury to their blood supply.

Non-surgical causes of hypoparathyroidism are much less common, but include an autoimmune condition (autoimmune polyendocrine syndrome), rare genetic defects, magnesium deficiency, or radiation therapy to the visceral space of the neck.

what are the effects of hypoparathyroidism?

Without adequate parathyroid hormone and the result of low blood calcium becomes low, an individual may experience numbness or tingling (termed paresthesias), most commonly first detected in the lips or fingertips. Cramping or spasm of muscles (known as tetany), may also occur. Progression to a very low calcium level risks development of seizures and electrical heart conduction abnormalities. Electrical abnormalities on an electrocardiogram (ECG or EKG) include prolongation of the time interval between the Q and the T waves (prolonged QTc), which rarely can progress to a potentially lethal problem termed Torsade de Pointe and ventricular fibrillation.

Long term consequences of hypoparathyroidism include increased risk for seizures and kidney problems, including kidney stones, decreased quality of life (especially a sense of “brain fog”), dry skin, and cataracts.

Is hypoparathyroidism temporary or permanent?

Hypoparathyroidism after surgery may be temporary or permanent. It is temporary about 75% of the time. Predicting whether post-operative hypoparathyroidism will resolve is not always possible, but several factors may help inform the situation while waiting for return of parathyroid function. One major clue is the assessment of the surgeon. If one or more parathyroid glands were seen at the time of surgery to be preserved and with a good vascular supply, this strongly favors resolution of any post-operative hypoparathyroidism. A blood draw showing any detectable parathyroid hormone after surgery is also a strong indicator that parathyroid function will normalize. Other factors such as the rate with which calcium levels drop after surgery may modify the prediction.

For a post-operative patient with hypoparathyroidism, initial management involves medical treatment to maintain safe blood calcium levels with supplemental calcium and possible vitamin D. Over days to weeks, periodic blood draws to check calcium and possibly parathyroid hormone levels allow the physician to gradually reduce supplements of calcium and vitamin D, anticipating full recovery.

If hypoparathyroidism does not resolve within a few months after surgery, it may be expected to be permanent. Treatment will then involve long-term medication, typically calcium and vitamin D supplementation. See below.

how is hypoparathyroidism treated?

The main treatment of hypoparathyroidism is calcium and/or vitamin D supplementation. For new hypoparathyroidism after surgery, calcium replacement or vitamin D can improve the low calcium and the associated symptoms. Checking blood magnesium and supplementing any deficiency helps the kidney retain calcium. Mild hypocalcemia may be treated with oral calcium. As the severity of hypocalcemia worsens, increasing doses given more frequently may be used. For additional boost in serum calcium, oral vitamin D may be given, also with dose and frequency according to need. More severe hypocalcemia may be treated with intravenous calcium gluconate, which typically requires being in a healthcare facility.

Repeated blood draws are used to assess the blood concentration of calcium, and possibly also albumin, parathyroid hormone level, and magnesium. The regimen of medications for treating low calcium may be gradually lessened as the calcium level improves.

In the case of hypoparathyroidism that does not improve in the weeks following surgery, treatment includes long-term vitamin D and calcium supplementation. Periodic monitoring of blood calcium is necessary, and the target calcium levels are at the lower limit of normal to miminize risk of kidney problems such as kidney stones and worsened kidney function. Kidney ultrasound examinations may also help in monitoring for associated kidney problems.

Replacing parathyroid hormone for treatment of hypoparathyroidism has advantages and disadvantages. The two types of replacement, one the full parathyroid hormone (recombinant hPTH), and the other a smaller protein containing only the active portion of the full hormone (teriparatide), are proteins, which means they cannot be taken by mouth because the body would break down the protein and digest it before it entered the blood stream. While having the advantage of replacing more exactly what is missing in hypoparathyroidism, the parathyroid hormone itself, these medications must be given either with subcutaneous injection or, in the case of teriparatide, with a pump delivery system.

Long term management of hypoparathyroidism is usually undertaken under the care of an endocrinologist.