What causes high calcium levels in the blood?

As a medical professional with expertise in endocrinology, I can provide insight into the causes of high calcium levels in the blood, also known as hypercalcemia. While parathyroid disease, particularly primary hyperparathyroidism, is a common cause, there are several other potential causes that can lead to elevated calcium levels. Here's a comprehensive look at the possible reasons: 1. Primary Hyperparathyroidism: This is the most common cause, where the parathyroid glands produce too much parathyroid hormone (PTH), leading to increased calcium levels. 2. Secondary Hyperparathyroidism: This occurs when the parathyroid glands produce more PTH in response to low calcium levels, often due to kidney disease or vitamin D deficiency. 3. Tertiary Hyperparathyroidism: This is a rare condition where the parathyroid glands become overactive even when calcium levels are normal, often after long-term kidney disease treatment. 4. Vitamin D Intoxication: Excessive intake of vitamin D can lead to hypercalcemia by increasing the absorption of calcium from the gut. 5. Cancer: Certain types of cancer, particularly those affecting the bones or those that produce PTH-related protein (PTHrP), can cause hypercalcemia. 6. Immobilization: Prolonged bed rest or inactivity can lead to an increase in calcium levels due to decreased bone resorption. 7. Thyroid Hormone Overreplacement: Taking too much thyroid hormone can increase the metabolic rate, which can lead to higher calcium levels. 8. Addison's Disease: This is a rare adrenal gland condition that can cause hypercalcemia. 9. Milk-Alkali Syndrome: This is a condition that results from consuming too much calcium and alkali, which can lead to hypercalcemia. 10. Granulomatous Diseases: Diseases like sarcoidosis can cause the body to absorb too much calcium. 11. Familial Hypercalcemia: There are genetic conditions that can cause high calcium levels. 12. Other Medications: Certain drugs, including some diuretics and lithium, can contribute to hypercalcemia. To determine the cause of high calcium levels, healthcare providers will typically perform a series of tests, including blood tests to measure calcium, PTH, and vitamin D levels, as well as imaging studies if cancer is suspected.

High calcium in the blood is due to parathyroid disease (hyperparathyroidism) almost all the time. High blood calcium (hypercalcemia) is never normal. All causes of high calcium are discussed, including what tests will determine the cause of the high calcium. No worries, high blood calcium is almost never cancer!