Hyperparathyroidism is where the parathyroid glands, which are in the neck near the thyroid gland, produce too much parathyroid hormone.

This causes blood calcium levels to rise (hypercalcaemia). Left untreated, high levels of calcium in the blood can lead to a range of problems.

Symptoms of hyperparathyroidism

Hyperparathyroidism usually causes few or no symptoms. The severity of symptoms doesn't always relate to the level of calcium in your blood.

For example, some people with a slightly raised calcium level may have symptoms, while others with high calcium levels may have few or no symptoms at all.

If you do have symptoms, they can be wide ranging and include:

• depression
• tiredness
• feeling thirsty and peeing a lot
• feeling sick and losing your appetite
• muscle weakness
• constipation
• tummy pain
• loss of concentration
• mild confusion

Left untreated, high blood calcium levels may cause:

• vomiting
• drowsiness
• dehydration
• confusion
• muscle spasms
• bone pain or tenderness
• joint pain
• irregular heartbeat
• high blood pressure (hypertension)

It can also cause a number of other possible complications, including:

• osteoporosis and bone fractures
• kidney stones and blockage, and kidney damage or failure
• peptic ulcers
• pancreatitis (inflammation of the pancreas)

In very severe cases of hyperparathyroidism, high calcium levels can lead to rapid kidney failure, loss of consciousness, coma, or serious life-threatening heart rhythm abnormalities.

But hyperparathyroidism is usually diagnosed at an early stage in the UK, and these complications are extremely rare.

Diagnosing hyperparathyroidism

It's important that hyperparathyroidism is diagnosed as soon as possible. Without treatment, it can gradually get worse and may lead to complications.

But in most cases, the condition is mild to moderate and remains stable for years.

Hyperparathyroidism is diagnosed after a blood test shows:

• high levels of parathyroid hormone
• high levels of blood calcium, often with low levels of phosphorus

A DEXA scan (a bone density X-ray) can help detect bone loss, fractures or bone softening, and X-rays, CT scans or ultrasound scans may show calcium deposits or kidney stones.

Causes of hyperparathyroidism

There are 2 main types of hyperparathyroidism:

• primary – when there's a problem within the parathyroid gland itself, usually a benign (non-cancerous) tumour of the gland
• secondary – when there's nothing wrong with the gland, but a condition like kidney failure or vitamin D deficiency lowers calcium levels, causing the body to react by producing extra parathyroid hormone

Tertiary hyperparathyroidism is a term that describes long-standing secondary hyperparathyroidism that starts to behave like primary hyperparathyroidism.

It's associated with very advanced kidney failure (usually requiring dialysis).

People with tertiary hyperparathyroidism are almost always under the care of kidney specialists.

Causes of primary hyperparathyroidism

In 4 out of 5 cases, primary hyperparathyroidism is caused by a non-cancerous tumour called an adenoma on one of the parathyroid glands.

Less commonly, it can occur if 2 or more parathyroid glands become enlarged (hyperplasia).

Very rarely, primary hyperparathyroidism can be caused by cancer of a parathyroid gland.

Women are twice as likely to develop primary hyperparathyroidism than men. Most women who develop it are 50 to 60 years of age.

Treating primary hyperparathyroidism

Surgery to remove the parathyroid gland is the only way of treating primary hyperparathyroidism. This cures about 97% of cases.

If your calcium levels are very high, you may need to be admitted to hospital urgently.

In this situation, dehydration needs to be corrected, usually with fluids given through an intravenous drip.

Medication called bisphosphonates may also be given to lower calcium. These are only used as a short-term treatment. Surgery will be needed once the calcium levels are stabilised.

For people who are unable to have surgery – for example, because of other medical conditions or they're too frail – a tablet called cinacalcet may be used to help control the condition.

Make sure you have a healthy, balanced diet.

You don't need to avoid calcium altogether. A lack of dietary calcium is more likely to lead to a loss of calcium from your skeleton, resulting in brittle bones (osteoporosis).

But you should avoid a high-calcium diet and drink plenty of water to prevent dehydration.

Medications such as thiazide diuretics (water tablets commonly used to treat high blood pressure) should be avoided because they can cause dehydration and raise calcium levels.

Treating secondary hyperparathyroidism

Treatment for secondary hyperparathyroidism depends on the underlying cause.

Low vitamin D is the most common cause and can be corrected with oral vitamin D (colecalciferol).

Kidney disease is another common cause – read more about treating chronic kidney disease.

Treating tertiary hyperparathyroidism

Cinacalcet may be used to treat tertiary hyperparathyroidism that occurs in very advanced kidney failure.