Hypoparathyroidism is a rare disorder in which the parathyroid glands in the neck secrete low levels of parathyroid hormone (PTH). Hypoparathyroidism results in abnormally low levels of calcium in the blood, adversely affecting many physiologic processes.
Parathyroid hormone works in conjunction with other hormones to regulate levels of calcium, phosphorus, and vitamin D in the blood and bone. When the parathyroid glands produce too little PTH, blood levels of calcium fall and phosphorous levels rise. The most common cause of hypoparathyroidism is injury to the parathyroid glands during thyroid or neck surgery. Other conditions that cause hypoparathyroidism include:
Why are calcium and phosphorus so important?
Calcium and phosphorus are the elements most abundant in the human body. Most of the body’s calcium is stored in the bones and teeth. The rest circulates through the bloodstream or resides in soft tissue. Calcium is important for normal functioning of almost every physiologic process. It affects nerve conduction, muscle contraction, forms cell membranes and regulates the activity of enzymes.
Only one percent of the total amount of calcium in the body is found outside of bone; however, this form of calcium is critical for communicating information among cells. For example, blood calcium stabilizes blood pressure and promotes normal brain function. In a healthy adult, the amount of calcium inside the cells is low when compared to the amount circulating in the blood. Hormones such as PTH stimulate the cell wall to allow an influx of calcium so that vital functions can be performed.
Phosphorus helps the body absorb and utilize calcium. In addition to aiding calcium in nerve conduction, muscle contraction and formation of cell membranes, phosphorus regulates the body’s pH levels and plays an important role in the development of genetic material. Phosphorus is just as important as calcium in the formation of strong bones and teeth.
With hypoparathyroidism, low production of PTH causes an imbalance: the calcium levels in your blood decrease (hypocalcemia) and serum phosphorus increases (hyperphosphatatemia).
Simply put, low levels of PTH disrupt the calcium/phosphorus balance. It’s the low level of circulating blood calcium that causes the symptoms of hypoparathyroidism.
Symptoms of hypoparathyroidism
Calcium supplies our bodies with the electrical energy needed for normal muscle contraction and nervous system function. Symptoms of hypoparathyroidism are related to dysfunction of the nerves and muscles. Symptoms that arise from hypocalcemia range from mild to severe.
During a physical exam, the physician may ask if you’ve experienced muscle spasms, particularly in the face or hands. A diagnosis of hypoparathyroidism is confirmed with a blood test that measures levels of calcium, phosphorus, magnesium and PTH. A urine test may also be ordered if it is suspected that the kidneys are excreting too much calcium.
The goal of treatment is to restore the delicate balance of the body's calcium and phosphorus levels. Generally, this is accomplished with supplementation of vitamin D and calcium carbonate. Vitamin D is prescribed because it helps the body absorb calcium.
As an adjunct to vitamin D and calcium, parathyroid hormone may be prescribed. Natpara® (parathyroid hormone) was recently granted orphan drug status by the US Food and Drug Administration to help control low blood calcium levels (hypocalcemia) in patients with hypoparathryoidism. The medication is injected once a day to help regulate the body’s calcium levels.
In addition, regularly scheduled blood tests are necessary to ensure that levels of vitamin D and calcium are maintained within normal ranges. Sometimes, a thiazide diuretic may be prescribed, as this type of drug has been shown to increase blood calcium levels. For relief of severe muscle spasms (tetany), calcium may be administered intravenously.
There is no cure for hypoparathyroidism; however supplements and lifestyle changes are generally all that’s needed to manage mild symptoms. Early diagnosis and treatment can help prevent complications.