Primary hyperparathyroidism is the most common cause of hypercalcemia, accounting for about 80% of cases. It occurs when the parathyroid glands produce too much parathyroid hormone (PTH), increasing calcium levels in the blood.

The most common cause of this is a benign tumor called a parathyroid adenoma, which develops in one of the parathyroid glands. Other less common causes include parathyroid hyperplasia, parathyroid cancer, and inherited genetic disorders.

Some types of cancer, such as multiple myeloma, lung cancer, breast cancer, and kidney cancer, can cause hypercalcemia by releasing substances that increase calcium levels in the blood.

Taking too much vitamin D supplements or having a disease that increases vitamin D levels in the body, such as sarcoidosis, can lead to hypercalcemia.

Prolonged immobilization, such as when a patient is bed-bound, can cause hypercalcemia by increasing bone resorption and calcium release.

Certain medications can cause high calcium levels, including:

• Certain supplements in excess (Vitamin D, Calcium, Vitamin A)
• Thiazide diuretics
• Lithium
• Theophylline toxicity

Other generic and acquired positions can lead to hypercalcemia complications, including hyperthyroidism, acromegaly, pheochromocytoma, adrenal insufficiency, and TPN.

Hypercalcemia can cause anorexia, constipation, nausea, and vomiting.

Patients with hypercalcemia often feel tired and weak, just like with many other electrolyte abnormalities.

High calcium levels lead to decreased concentration ability of the kidneys and subsequent urinary frequency/dehydration.

Chronic high calcium levels in the urine can lead to nephrolithiasis (kidney stones).

Hypercalcemia can affect the central nervous system, leading to cognitive impairment and even confusion, stupor, or coma.

Hypercalcemia can affect the heart’s electrical conductivity, leading to arrhythmias, which may cause palpitations, chest pain, shortness of breath, dizziness, or syncope. This is generally not as common with hypercalcemia as with other electrolyte abnormalities.

Chronic hypercalcemia can lead to the deposition of calcium in heart valves, coronary arteries, and the heart muscle itself. This can also lead to hypertension and heart failure.

Bone pain can be a symptom of high calcium due to malignancy or primary hyperparathyroidism.

• HR: May be irregular (indicating an arrhythmia)
• BP: May be increased

• General: May appear weak or fatigued

• Heart: May be irregular if arrhythmia present
• Lungs: Clear to auscultation

• Abdomen: May have abdominal tenderness
• Extremities: May have bone pain or tenderness, may have extremity weakness

GENERAL MEASURES

Mild hypercalcemia often does not require any specific calcium-lowering therapies, but instead can usually be managed by:

• Treating dehydration
• Decreasing bed rest
• Avoiding high-calcium diets
• Avoiding medications that increase calcium levels
• Thiazide Diuretics
• Lithium
• Calcium supplements
• Vitamin D supplements

Patients who have moderate to severe hypercalcemia often are volume depleted. This helps to correct the hypovolemia and increase calcium excretion in the urine. NS or LR given at 200-300ml/hr and then adjusted to a urine output of 100-150ml/hr is recommended for 24-48 hours until the volume depletion is corrected.

Calcitonin is a hormone that can lower calcium levels in the blood by decreasing bone resorption. This is usually reserved for severe hypercalcemia with neurologic symptoms like decreased mental status. The recommended dose is 4 units/kg SQ or IM every 12 hours for 24-48 hours.

These medications can reduce bone resorption and lower calcium levels in the blood. Bisphosphonates are used for longer-term control of hypercalcemia, especially when related to malignancy. If given IV for severe hypercalcemia in the hospital, Zalendronic acid is recommended 4mg IV over 15 minutes. This can be repeated in 7 days if needed.

Denosumab is a monoclonal antibody that is sometimes used if Bisphosphonates are not effective or not able to be used. There is a higher risk of hypocalcemia occurring with this medication, so it is avoided when possible.

This is primarily only given if the hypercalcemia is caused by lymphoma, sarcoidosis, or other granulomatous disease that increases calcitriol production and subsequently increases calcium absorption.

In severe cases, dialysis may be needed to remove excess calcium from the blood, especially if they also have heart failure or severe renal failure.

Underlying conditions, such as cancer, may need to be treated to improve calcium levels.

Serum calcium levels should be monitored regularly to assess treatment response and to identify potential complications such as hypocalcemia.

Measuring parathyroid hormone helps determine the etiology of the high calcium levels. If PTH is elevated, this points to primary hyperparathyroidism. If it is low, it is likely not from hyperparathyroidism.

The nurse should monitor laboratory values such as serum calcium, magnesium, and phosphate levels and liver and kidney function tests to assess for complications and monitor treatment progress.

Possible hypercalcemia complications include arrhythmias, so continuous telemetry monitoring, as well as occasional 12-lead ECGs are indicated.