When calcium levels in the blood become too high, a condition known as hypercalcemia occurs. While high calcium can signal cancer, it’s crucial to understand it’s not the only cause and requires medical evaluation. This article explores the connection between high calcium and cancer, as well as other potential causes for this elevation.
Understanding Hypercalcemia
Hypercalcemia refers to an abnormally high concentration of calcium in the bloodstream. For adults, a normal blood calcium level typically ranges from 8.5 to 10.2 milligrams per deciliter (mg/dL) or 2.1 to 2.6 millimoles per liter (mmol/L), though specific laboratory ranges can vary slightly.
Calcium is an abundant mineral, with most of it stored in bones and teeth, providing structural support. The remaining calcium circulates in the blood, where it performs several essential functions. This circulating calcium is involved in nerve signal transmission, muscle contraction, and blood clotting. It also plays a role in maintaining a regular heartbeat. When calcium levels become elevated, these processes can be disrupted, potentially leading to health problems.
The body carefully regulates calcium levels through hormones to maintain this balance.
Cancer’s Role in Elevated Calcium
Cancer can lead to hypercalcemia through several distinct mechanisms, making it a significant cause of this condition. One common way is through bone metastasis, where cancer cells spread to the bones. Once in the bone, these malignant cells can stimulate osteoclasts, which are cells responsible for breaking down bone tissue. This breakdown releases calcium directly into the bloodstream, increasing blood calcium levels.
Another mechanism involves the production of parathyroid hormone-related protein (PTHrP) by certain tumors. PTHrP mimics the action of parathyroid hormone (PTH), a natural hormone that regulates calcium. When PTHrP is released by cancer cells, it causes the bones to release more calcium and signals the kidneys to reabsorb more calcium rather than excrete it. Cancers frequently associated with PTHrP production include squamous cell carcinomas, such as those found in the lung, head, and neck, as well as breast cancer and kidney cancer. This phenomenon, known as humoral hypercalcemia of malignancy, is a paraneoplastic syndrome, meaning it is caused by substances secreted by the tumor, not by the tumor’s direct presence in the affected organ.
Some lymphomas and other granulomatous diseases can also cause hypercalcemia by producing an active form of vitamin D, specifically 1,25-dihydroxyvitamin D. This production of active vitamin D occurs outside the kidneys, often by macrophages associated with the tumor or granulomas. Elevated levels of active vitamin D enhance the absorption of calcium from the intestines.
Other Reasons for High Calcium
While cancer is a notable cause, hypercalcemia can also stem from several non-cancerous conditions. Primary hyperparathyroidism stands out as the most frequent non-cancerous cause of elevated calcium. This condition occurs when one or more of the four tiny parathyroid glands, located in the neck near the thyroid, become overactive and produce too much parathyroid hormone (PTH). Excess PTH leads to increased calcium release from bones and greater reabsorption of calcium by the kidneys, resulting in high blood calcium levels.
Excessive intake of vitamin D or vitamin A supplements can also cause hypercalcemia. Taking very high doses of vitamin D can lead to an overload, increasing calcium absorption from the gut. Similarly, too much vitamin A can promote calcium release from bones.
Certain medications have been linked to elevated calcium levels. These include thiazide diuretics and lithium, used in the treatment of bipolar disorder. Other medications like teriparatide, estrogens, and tamoxifen can also contribute to hypercalcemia.
Dehydration can temporarily elevate calcium levels by concentrating the blood. This means there is less fluid volume, making the existing calcium appear more concentrated. Additionally, other medical conditions, such as sarcoidosis, can cause hypercalcemia due to the abnormal production of active vitamin D by immune cells. Prolonged immobility can also lead to increased calcium release from bones.
Recognizing Symptoms and Next Steps
Symptoms of hypercalcemia can vary widely, ranging from mild or even absent in early stages to severe in more advanced cases. Common general symptoms include fatigue, increased thirst, and frequent urination as the kidneys work harder to filter excess calcium. Digestive issues such as constipation, nausea, and vomiting may also occur.
As calcium levels rise, individuals might experience bone pain or muscle weakness because calcium is drawn from the bones. Neurological symptoms can manifest as confusion, difficulty concentrating, or depression. More severe hypercalcemia can lead to kidney stones, which cause significant pain, and in rare instances, can affect heart rhythm.
Given that symptoms can be vague and overlap with many other conditions, it is important to consult a doctor if you experience persistent symptoms that could indicate high calcium levels. A healthcare professional can diagnose hypercalcemia through blood tests that measure calcium levels, often as part of routine metabolic panels. Further tests, such as parathyroid hormone (PTH) levels, PTHrP, and vitamin D levels, can help determine the underlying cause. Treatment for hypercalcemia focuses on addressing the root cause, which may involve hydration, discontinuing certain medications, or specific treatments for conditions like primary hyperparathyroidism or cancer.