Underactive parathyroid gland
The parathyroid glands are small, pea-sized glands, located in the neck just behind the butterfly-shaped thyroid gland. Two parathyroid glands lie behind each 'wing' of the thyroid gland (there are four in total). The parathyroid glands release a hormone called parathyroid hormone. This hormone helps to control the levels of calcium in the bloodstream.
Hypoparathyroidism is a rare condition in which not enough parathyroid hormone is produced, which results in low calcium levels in the body.
Most commonly, hypoparathyroidism is caused by damage to parathyroid glands during neck surgery. The commonest non-surgical cause is destruction of the parathyroid glands by the body’s immune system. In very rare cases, the parathyroid glands are destroyed by irradiation, usually as a result of treatment of a tumour, or rare diseases that attack the parathyroid glands.
Some people are born with hypoparathyroidism (congenital) and sometimes the cause is unknown (idiopathic).
The symptoms depend on the level of calcium in the bloodstream and the rate at which the calcium level has dropped. In mild cases of hypoparathyroidism, there may be no symptoms at all. Often the symptoms are not specific to the condition, such as tiredness, irritability, mood swings, anxiety and depression. There may be muscle pains, abdominal pain, tingling of the fingers, toes or face, numbness around the mouth, twitching of the face muscles, contraction or tightening of the muscles of the hands and feet, fits, fainting, confusion, headaches, tiredness, brittle nails, dry skin and hair, and uncontrolled spasms that cause muscle cramps.
When calcium levels fall very fast or very low, there may be fits (known as seizures) or spasm of the muscles in the airways causing noisy and difficult breathing.
After complete removal of the thyroid glands (total thyroidectomy), the risk of permanent hypoparathyroidism is between 1% to 3%. All other causes of hypoparathyroidism are very rare.
Very rarely, there are inherited forms of hypoparathyroidism due to genetic causes. A family history of low calcium suggests a genetic cause. Sometimes there may be other associated conditions, such as weakness of the immune system, deafness and thrush. The pattern of inheritance can be complicated – an affected parent will not necessarily pass on the condition to his or her children. For patients with hypoparathyroidism due to genetic causes, specific advice and counselling should be available from a specialist in genetics.
Initially, diagnosis is made by measuring the parathyroid hormone and calcium levels in the blood. The patient’s GP or specialist may also check kidney function and levels of phosphate, magnesium and vitamin d in the bloodstream.
The aim of treatment is to relieve symptoms and minimise complications. All patients need adequate calcium intake in their diet (1.0–1.5 g per day). In most cases, a satisfactory level of calcium in the blood is maintained by taking a combination of calcium, and vitamin D tablets, usually in the form of calcitriol or alphacalcidol.
Treatment and monitoring can be as an outpatient. In very sudden, severe cases (for example if the condition is causing fits or restricting breathing), urgent hospital treatment may be needed to correct calcium levels using an intravenous drip. Hypoparathyroidism is one of the rare hormone conditions where no direct medical method is currently available for replacing the parathyroid hormone, although research is underway to find a solution to this problem.
There are no direct side-effects to treatment as long as not too much calcium is replaced. Regular monitoring every 6 to 12 months is required. Simple urine tests may be needed to measure the amount of calcium passed through the kidneys. Too much calcium in the urine can lead to kidney stones or deposits of calcium in the kidneys (known as nephrocalcinosis).
It is important to recognise that long-term physical complications are uncommon in most patients who are treated for hypoparathyroidism, although some patients report a reduced quality of life and poorer general wellbeing, even after treatment.
Long-standing, uncorrected hypoparathyroidism may lead to deposits of calcium in the base of the brain. This can result in abnormalities in body movement or memory loss, but can also be symptom-free.
Other rare complications include cataracts and an inflammation of the eye known as keratoconjunctivitis. Defective teeth (especially in childhood), thin skin, brittle nails and hair loss are also recognised as long-term complications of hypoparathyroidism.
In very rare cases, untreated hypoparathyroidism may cause heart failure.
Last reviewed: Jan 2015