Hypoparathyroidism is a rare disease characterized by lower-than-normal levels of parathyroid hormone (PTH) — the most important regulator of blood calcium levels — in the body.
PTH, produced by the four small parathyroid glands found in the neck, plays a key role in regulating the balance of two minerals — calcium and phosphorus. As such, low levels of PTH result in hypocalcemia (low levels of calcium) and high levels of phosphorus in the blood, which can cause a wide range of symptoms, including muscle cramps, pain, and twitching.
Causes
Hypoparathyroidism has several causes, each of which results in a different type of the disease.
Acquired hypoparathyroidism: Commonly caused by damage to or removal of the parathyroid glands. The glands can be damaged by accident during surgery to the head or neck, or during chemotherapy or radiation therapy (used to treat cancer). Due to its role in the function of the parathyroid glands, low levels of magnesium also cause some cases of acquired hypoparathyroidism.
Autoimmune hypoparathyroidism: This type occurs when the immune system wrongly attacks the parathyroid glands, which makes them stop producing PTH. Autoimmune hypoparathyroidism can exist as part of an inherited condition called autoimmune polyendocrine syndrome type 1, which often begins in childhood or adolescence, that affects many of the body’s organs.
Congenital hypoparathyroidism: It happens when people have hypoparathyroidism from birth, as a result of mutations in the genes involved in the production of PTH. This type of hypoparathyroidism also may occur in people who are born without parathyroid glands. It may be temporary or permanent. An example of temporary hypoparathyrodism is seen in infants whose mothers have excess calcium in the blood due to hyperparathyroidism, which suppresses PTH production in the fetus.
Idiopathic hypoparathyroidism: This form of hypoparathyroidism means that insufficient PTH secretion is not secondary or acquired — it does not have a known cause.
Familial isolated hypoparathyroidism: This disease type is caused by genetic mutations, as in the calcium-sensing receptor (CASR) gene, and is passed down to the offspring. It occurs in the absence of other endocrine diseases or developmental problems.
Symptoms
Symptoms of hypoparathyroidism are mainly due to the effects of low levels of calcium in the blood.
While mild symptoms may not need any treatment, severe symptoms may appear quickly and require urgent therapy. Possible symptoms include paresthesia or a tingling sensation in the fingers, toes, and lips, as well as cramps in the legs, feet, or face. Spasms and aches in muscles, fatigue, generalized weakness, mood changes, and seizures are other possible symptoms. People with hypoparathyroidism also may have dry skin, irregular hair loss, weak nails, depression, and irritability.
Diagnosis
Hypoparathyroidism is usually diagnosed through a physical assessment, a review of family history, and specific lab tests including blood and urine analyses.
Blood tests examine the levels of several minerals and molecules, including PTH, calcium, phosphorus, magnesium, and vitamin D. Notably, vitamin D — whose levels are regulated by PTH — helps regulate the levels of calcium and phosphorus in the blood.
Urine tests are used to determine the amount of calcium being excreted.
Regular lab tests may be needed during treatment to ensure that levels remain stable and within normal ranges.
Treatment
Treatment of hypoparathyroidism aims at easing symptoms and normalizing levels of calcium and phosphorus. Standard treatment may include:
- Oral supplements of calcium and activated vitamin D (calcitriol). While oral calcium supplements increase blood calcium levels, vitamin D stimulates the absorption of calcium in the gut. Magnesium supplements also may be recommended in cases of insufficient blood magnesium.
- Thiazide diuretics. In patients whose calcium levels do not respond to treatment with oral supplements, diuretics (medications that increase the flow of urine) will decrease the amount of calcium lost through the urine by helping the kidneys absorb this mineral to the blood.
- PTH replacement therapy (Natpara). This is the only PTH replacement therapy approved by the U.S. Food and Drug Administration for people with hypoparathyroidism. This synthetic form of PTH, intended to be used in combination with calcium and vitamin D supplements, is injected under the skin to reestablish adequate calcium levels. Natpara was recalled in 2019 in the U.S. due packaging issues, and Takeda is still working with authorities to resolve the matter.
Patients with hypoparathyroidism may be advised to change their diet to include foods high in calcium — examples include dairy products, leafy vegetables, and breakfast cereals. It also may be urged that hypoparathyroidism patients avoid products high in phosphorus, such as carbonated soft drinks, while limiting the consumption of meats and whole grains.
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Last updated: April 5, 2021
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