Hypercalcemia is a condition that results from a high concentration of calcium in the blood. Calcium is needed for the normal functioning of muscles, organs, cells, and nerves; it is also essential for bone health and blood clotting.

Most of the calcium in the body goes to the bone, but some are also needed in the blood; however, when it becomes too much, it can result in hypercalcemia, making it hard for the body to carry out normal functions.

Causes

The interaction between vitamin D, calcium, and parathyroid hormone (PTH) regulates the calcium levels in the body. The parathyroid hormone controls the amount of calcium that goes into the bloodstream from the kidneys, bones, and intestines. When the blood calcium level is low, the PTH increases so that more calcium can be produced, but when blood calcium is high, PTH decreases to reduce the amount of calcium in the blood. 

Your body also produces calcitonin, a hormone that reduces blood calcium when it is high. So here are some common causes of hypercalcemia.

• The hyperactiveness of the parathyroid glands makes them produce too much calcium.
• An enlargement of one or more of the parathyroid glands.
• A tumour on one of the parathyroid glands. 
• Too much calcium and vitamin D intake from diet and supplements.
• Chronic kidney disease or kidney failure.
• Some health problems, such as tuberculosis, Paget disease, and sarcoidosis.
• Certain kinds of cancers, like breast and lung cancer.
• An inherited condition that affects the body’s ability to manage calcium.
• Medicines such as lithium and thiazide diuretics (water pills).

Symptoms of Hypercalcemia

The symptoms of hypercalcemia are usually mild, but more severe cases can give symptoms related to the parts of the body it is affecting. For example: 

• Excess calcium gives the kidneys more work to filter it and can cause frequent urination and thirst. 
• Bones can become weak, causing bone pain and muscle weakness because the bulk of the excess calcium in the blood is usually gotten from the bones. 
• Hypercalcemia can also cause nausea, vomiting, stomach upset and constipation. 
• Severe hypercalcemia can interfere with heart functions and cause palpitations, fainting, signs of cardiac arrhythmia and other heart problems. 
• Hypercalcemia can also interfere with brain functions, resulting in fatigue, forgetfulness, confusion, lethargy, and depression. 

Treatment

Treatment of hypercalcemia depends on its severity and the underlying cause of the condition. In mild cases, you may not need immediate treatment; your healthcare provider may tell you to drink more water, stop taking or lower your dose of calcium supplements, stop taking or lower your dose of calcium-rich antacid tablets, and switch to a non-thiazide blood pressure medication. 

For hypercalcemia due to a hyperactive thyroid gland, your doctor may recommend surgery to remove the affected thyroid gland. For hypercalcemia due to cancer, you can be placed on medications like bisphosphonates and sometimes denosumab, which is a bone-strengthening medicine for patients who do not respond to bisphosphonates.

If the hypercalcemia is severe, with many symptoms that prevent the patient from living a normal life, your doctor may recommend hospitalisation for IV fluids and other treatments.