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What Causes Hypercalcemia?

Reviewed by Melinda Ratini, DO, MS on January 15, 2020

If your doctor tells you that you have hypercalcemia, it means you have too much calcium in your blood. Some medical conditions can cause it. So can the kind of lifestyle you have, your genes, and certain medications.

You may not notice any symptoms if you have a mild case of hypercalcemia. But as your body tries to get rid of the extra calcium, you might pee a lot and get really thirsty. If your calcium levels are very high, you could get nervous system problems, including becoming confused and eventually unconscious.

You'll usually find out that you have hypercalcemia through a blood test. If you don't get it treated, high levels of calcium in your blood can lead to bone loss, kidney stoneskidney failure, and heart problems.

Your doctor can help you get your calcium levels back to normal and figure out why they're out of whack in the first place.

Overactive Parathyroid Glands (Hyperparathyroidism)

Overactive parathyroid glands are the most common cause of hypercalcemia. When these glands are working right, they release parathyroid hormone (PTH) when your blood calcium levels get low. The release of this hormone helps your body absorb more calcium and lessens the amount you lose when you pee. It also pulls calcium from your bones and puts it into your blood.

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But if you have overactive parathyroid glands, your body pumps out more PTH than you need. This can happen if they grow too big or a noncancerous tumor forms on one or more of your glands.

If hyperparathyroidism is the cause of your high calcium, you may also get:

You may not need treatment if you have mild hypercalcemia. But your doctor will monitor your health. Most likely, they'll check your blood calcium and blood pressure every 6 months. And they'll run tests on your kidneys once a year. You may need to get a bone density test every 1-3 years.

They may also tell you to:

You may need to take drugs called calcimimetics. They lower your PTH levels. In more serious cases, a surgeon may take out your parathyroid gland (or glands).

If your calcium levels are very high, you'll need to go to the hospital to get fluids and medicine called diuretics through your veins. This can treat hypercalcemia fast.

Cancer

Around 10%-30% of people with cancer may get hypercalcemia. That's because cancer can:

  • Cause your bones to break down and send calcium into your blood
  • Mimic your parathyroid hormone, which triggers the release of calcium from your bones
  • Affect your kidneys, which can lower the amount of calcium you get rid of when you pee

The most common cancer types that cause hypercalcemia include:

  • Lung cancer
  • Kidney cancer
  • Breast cancer
  • Multiple myeloma (a blood cancer that starts in bone marrow)

Your cancer or the treatment you get for it can share symptoms with hypercalcemia, such as feeling sick or throwing up. If you get dehydrated, your kidneys can't get rid of calcium very well. Your doctor may give you fluids through your vein.

Hypercalcemia from cancer can be hard to manage. It helps to treat your cancer. But you may need drugs to slow the release of calcium from your bones, including:

  • Bisphosphonates -- given through your veins
  • Denosumab (Prolia, Xgeva) -- as an injection

Supplements

If you take really high doses of vitamin A or D, you may absorb too much calcium. Overuse of calcium-containing antacids can also lead to hypercalcemia.

Your doctor will probably ask you to stop taking these supplements. If your vitamin D levels are really high, you may need to take steroid pills, like prednisone, for a short time.

Medication

Blood pressure drugs like thiazide diuretics can lower the amount of calcium that leaves your body when you pee. They may also make your parathyroid problems worse.

More than 20% of people who take lithium get hypercalcemia. Experts aren't sure why this happens. They think it's because the drug affects your parathyroid glands and the amount of PTH they make.

Your doctor may switch your medicine. If you need to stay on these drugs, they may give you medication to lower the amount of calcium in your blood.

Genetics

If you inherit a certain gene, your body misjudges how much calcium is in your blood. You'll send out more PTH than you need. It happens if you have a condition called familial hypocalciuric hypercalcemia (FHH). But in most cases, you won't have any symptoms or need treatment.

Your doctor may want to monitor your health. It's not common, but FHH can cause inflammation in your pancreas or calcium to build up in other parts of your body.

Less Common Causes

Health conditions. Lung diseases like tuberculosis and sarcoidosis can raise your blood levels of vitamin D. In turn, your gut will absorb more calcium. Paget's disease and an overactive thyroid are also linked to hypercalcemia.

Inactivity. Your bones release calcium if you don't put your body weight on them. This can happen if you're paralyzed or you have another illness that keeps you in bed for a long time. Not getting enough exercise may also make hyperparathyroidism worse.

Serious dehydration. Your kidneys can't get rid of calcium if you don't have enough fluid in your body. An easy way to know if you're dehydrated is to look at your urine. You want it to be light yellow, not a shade of dark orange. You should drink fluids until you're not thirsty. Call a doctor if you have diarrhea or you throw up for a long time and can't keep liquids down.

WebMD Medical Reference

Sources

SOURCES:

Cleveland Clinic: "Hypercalcemia," "Hyperparathyroidism."

Mayo Clinic: "Hypercalcemia," "Urine Color," "Dehydration."  

Merck Manuals: "Hypercalcemia (High Level of Calcium in the Blood.)"

John Wayne Cancer Institute: "Parathyroid Disease and Hyperparathyroidism; Hypercalcemia."

Turkish Journal of Surgery: "Primary hyperparathyroidism."

Canadian Family Physician: "Cancer-related hypercalcemia."

Cancer.net: "High Calcium Levels or Hypercalcemia."

The Journal of Clinical Endocrinology & Metabolism: "Thiazide-Associated Hypercalcemia: Incidence and Association With Primary Hyperparathyroidism Over Two Decades," "Physical Activity and the Risk of Primary Hyperparathyroidism." 

The Mental Health Clinician: "Lithium-induced hypercalcemia with normal parathyroid hormone: A case report."

World Journal of Surgery: "Lithium-Associated Hypercalcemia: Pathophysiology, Prevalence, Management."

Current Opinion of Endocrinology, Diabetes, and Obesity: "Familial hypocalciuric hypercalcaemia: a review."

National Center for Advancing Translational Sciences (GARD): "Familial hypocalciuric hypercalcemia."

UpToDate: “Hypercalcemia of malignancy: Mechanisms.”

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