This option should be considered by a patient and his or her family in advance, before symptoms of hypercalcemia occur. Normal calcium regulation Healthy people consume about the same amount of calcium in their diet as their bodies lose in urine, feces, and sweat. Hypercalcemia associated with cancer disrupts the body's ability to maintain a normal level of calcium. Kidney function Normal, healthy kidneys are able to filter large amounts of calcium from the blood, excrete the excess not needed by the body, and retain the amount of calcium the body does need. However, hypercalcemia may cause such high levels of calcium in the body that the kidneys are overworked and become unable to excrete the excess.
Some tumors produce a substance that can cause the kidneys to excrete too little calcium.
This results in a large amount of urine being produced, which then causes dehydration. Dehydration may lead to appetite loss, nausea, and vomiting which make the dehydration worse. Inactivity caused by weakness and tiredness may increase the amount of calcium in the blood by increasing the amount of calcium that is absorbed from the bones. Calcium deposits may collect in the kidneys, causing permanent damage. Causes The main causes of hypercalcemia due to cancer are an increase in the amount of calcium absorbed from the bones, and an inability of the kidneys to excrete excess calcium.