Overproduction of parathyroid hormone, which may lead to a high level of calcium in the blood

  • More common over the age of 50
  • More common in females
  • In some cases, the condition is inherited
  • Lifestyle is not a significant factor

Parathyroid hormone (PTH), which is produced by four pea-sized parathyroid glands embedded in the thyroid tissue, helps to regulate the body’s calcium levels. Overproduction of PTH is called hyper-parathyroidism and leads to high calcium levels in the blood. The condition rarely develops before the age of 50 and is much more common in women.

What are the causes?

The most common cause of hyperparathyroidism is a tumour in one or more of the four parathyroid glands. In some cases, development of parathyroid tumours is associated with the inherited disorder multiple endocrine neoplasia, in which tumours form in several endocrine glands. Parathyroid tumours are rarely cancerous.

The parathyroid glands may become enlarged and overproduce PTH in an attempt to compensate for disorders that cause a low level of calcium in the blood, such as chronic kidney failure. In these cases, the condition is called secondary hyperparathyroidism.

What are the symptoms?

A slightly raised level of calcium in the blood due to hyperparathyroidism may not cause obvious symptoms. However, people with a very high calcium level may develop the following symptoms:

  • Abdominal pain.

  • Nausea and vomiting.

  • Constipation.

  • Increased thirst and passing of urine.

  • Depression.

An abnormally high level of calcium in the blood may also lead to dehydration, confusion, and unconsciousness, and it can be life-threatening. Serious complications of hyperparathyroidism include the formation of kidney stones, due to a build-up of calcium, and bone fractures, resulting from calcium gradually leaking out of the bone into the bloodstream.

What might be done?

If you develop the symptoms of hyper-parathyroidism, your doctor is likely to arrange for you to have blood tests to assess your kidney function and check for raised levels of calcium and PTH. If you have not experienced symptoms, hyperparathyroidism is usually detected by chance during a routine checkup. Sometimes, the condition is diagnosed during investigations to look for the cause of kidney stones.

You may not require treatment if the level of calcium in your blood is only slightly raised; however, your blood calcium level and kidney function will need to be monitored annually. If your calcium levels are very high, you will be given fluids and drugs intravenously in hospital to lower blood calcium.

If a parathyroid tumour is accompanied by high blood calcium levels, the affected parathyroid gland will be removed surgically. You may need calcium supplements immediately after surgery, but body calcium levels usually return to normal after a few days. The underlying disorder causing secondary hyperparathyroidism will be treated if possible; alternatively, some of the parathyroid glands may be removed surgically.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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