Calcium is an essential mineral that keeps our bones strong and allows our muscles, nerves, and heart to work properly. But just like most things in life, too much of a good thing can be bad. When calcium levels in the blood become too high, a condition called hypercalcemia can develop. One of the most common causes of hypercalcemia is hyperparathyroidism — a condition where the parathyroid glands in the neck become overactive.

What are the parathyroid glands?

Most people are familiar with the thyroid gland, but fewer know about the parathyroid glands. These are four tiny glands, each about the size of a grain of rice, located behind the thyroid. Their main job is to control calcium levels in the body. They do this by releasing parathyroid hormone (PTH), which signals the bones to release calcium into the bloodstream, helps the intestines absorb calcium from food, and prompts the kidneys to hold on to calcium instead of flushing it out.

How common is it?

Hyperparathyroidism is not extremely rare. In fact, it is considered one of the more common causes of high blood calcium levels. It is estimated to affect about 1 in 1,000 people, and it is more common in women, especially those over the age of 50. Some people may go for years without knowing they have it because early symptoms can be mild or mistaken for other things.

Causes of hypercalcemia and hyperparathyroidism

Hypercalcemia can have several causes, but when it is due to hyperparathyroidism, it usually means that one or more of the parathyroid glands have developed a small, non-cancerous growth called an adenoma. This growth causes the gland to pump out too much PTH, leading to too much calcium in the blood.

Other causes of hypercalcemia include:

• Certain cancers, like lung or breast cancer

• Overuse of calcium or vitamin D supplements

• Some medications, like thiazide diuretics

• Prolonged immobility, which can cause calcium to leak from bones

But among these, primary hyperparathyroidism is the leading cause of high calcium levels detected during routine blood tests.

Symptoms to watch out for

The tricky part about hyperparathyroidism is that many people don’t have obvious symptoms at first. When symptoms do appear, they can vary widely and may include:

• Fatigue and weakness

• Frequent urination and dehydration

• Abdominal pain, nausea, or constipation

• Bone pain or fractures from weakened bones

• Kidney stones

• Memory problems, depression, or difficulty concentrating

How is it diagnosed?

Doctors usually detect hypercalcemia through routine blood tests that show elevated calcium levels. If this happens, they will often check the parathyroid hormone (PTH) level. A high calcium level along with a high PTH level strongly points to hyperparathyroidism.

Additional tests like bone mineral density scans, kidney ultrasounds, or special imaging of the neck and chest to locate overactive parathyroid glands may also be done.

Treatment options