Hypercalcemia is a condition where the level of calcium in the bloodstream is above the normal range. While it can arise from various medical conditions, it is sometimes observed in individuals with cancer. This connection highlights how cancer can influence the body’s calcium regulation processes. This article explores high blood calcium and its relationship with different types of cancer.
Understanding High Blood Calcium
Calcium plays many roles in the body, supporting bone health, nerve function, and muscle contraction. Blood calcium levels are carefully regulated, typically ranging between 8.5 to 10.5 milligrams per deciliter (mg/dL) or 2.1 to 2.6 millimoles per liter (mmol/L). When calcium levels exceed this upper limit, it is considered hypercalcemia.
Elevated calcium levels can lead to a range of physical symptoms that might develop gradually. Common signs include feeling unusually tired or weak, experiencing nausea, vomiting, or constipation. Individuals might also notice increased thirst and more frequent urination. As calcium levels rise further, symptoms can progress to confusion, memory problems, or even muscle weakness and bone pain.
How Cancer Causes High Blood Calcium
Cancer can disrupt the body’s calcium balance through several distinct biological pathways. One common mechanism is humoral hypercalcemia of malignancy (HHM), where tumor cells produce and secrete parathyroid hormone-related protein (PTHrP). This protein mimics natural parathyroid hormone, signaling bones to release calcium and kidneys to reabsorb more, thereby increasing blood levels.
Another way cancer causes high calcium is through osteolytic metastases, where cancer cells spread to the bones. These metastatic cells release factors that stimulate osteoclasts, which are cells responsible for breaking down bone tissue. As bone is broken down, the calcium stored within it is released directly into the bloodstream.
Beyond these primary mechanisms, other pathways exist. For instance, some lymphomas can cause hypercalcemia by producing calcitriol, an active form of Vitamin D, which enhances calcium absorption from the intestines.
Cancers Commonly Associated with High Blood Calcium
Many types of cancer can lead to elevated blood calcium levels, with some associations being more frequent than others. Multiple myeloma, a cancer affecting plasma cells in the bone marrow, often causes hypercalcemia due to its direct destruction of bone tissue. The malignant plasma cells activate osteoclasts, leading to significant bone breakdown and calcium release into the blood.
Breast cancer is another frequent cause of hypercalcemia, particularly when it has spread to the bones. The presence of breast cancer cells in bone tissue stimulates osteoclast activity, contributing to the release of calcium.
Lung cancer, especially the squamous cell carcinoma subtype, is commonly linked to humoral hypercalcemia of malignancy because these tumors frequently secrete PTHrP. Kidney cancer, specifically renal cell carcinoma, is also known to produce PTHrP, leading to elevated calcium levels. Similarly, head and neck squamous cell carcinomas are often associated with PTHrP secretion, contributing to hypercalcemia.
Lymphomas, a group of cancers affecting the lymphatic system, can cause high blood calcium through increased production of calcitriol, which boosts calcium absorption. Other solid tumors, such as prostate or thyroid cancer, can also lead to hypercalcemia if they develop extensive metastases in the bones.
Managing High Blood Calcium in Cancer Patients
Detecting high blood calcium in cancer patients typically involves a simple blood test to measure the calcium concentration. Once hypercalcemia is confirmed, immediate management focuses on reducing calcium levels and alleviating symptoms. Intravenous fluids are often administered to help dilute calcium in the blood and promote its excretion through the kidneys.
Medications are also used to control calcium levels and prevent further bone breakdown. Bisphosphonates, such as zoledronic acid or pamidronate, are commonly given intravenously to inhibit osteoclast activity and reduce calcium release from bones. Calcitonin is another medication that can provide a rapid, though temporary, reduction in blood calcium.
For long-term control of hypercalcemia, addressing the underlying cancer is a primary approach. This involves specific treatments like chemotherapy, radiation, or targeted therapies to manage the disease causing the calcium imbalance.