Calcium is the most abundant mineral in the human body, and is critical to good health. It is not only a component of bones and teeth, but is also essential for blood clotting and necessary for muscle and nerve functions. If the level of calcium in the body becomes too low (hypocalcemia) or too high (hypercalcemia), serious medical problems can occur.
Hypercalcemiais an abnormally high level of calcium in the blood, usually more than 10.5 milligrams per deciliter of blood. Symptoms include loss of appetite, nausea, vomiting, constipation, and abdominal pain. If the kidneys are involved, the individual will have to urinate frequently during both the day and night and will be very thirsty. As the calcium levels rise, the symptoms become more serious. Stones may form in the kidneys and waste productscan build up. Blood pressure rises and the heart rhythm may change. Muscles become increasingly weak. The individual may experience mood swings, confusion, psychosis, and eventually, coma and death.
Ten to twenty percent of all persons with cancer have hypercalcemia. In fact,it is the most common life-threatening metabolic disorder associated with cancer. Cancers of the breast, lung, head and neck, kidney, and blood are frequently associated with hypercalcemia. It is seen most often in patients with tumors of the lung (25-35%) and breast (20-40%), according to the National Cancer Institute. Cancer causes hypercalcemia in two ways. First, if a tumor grows into the bone, it destroys calcium-containing bony tissue (osteolysis), which is then reabsorbed by the body. Secondly, substances secreted by cancer cells can increase calcium levels (humoral hypercalcemia of malignancy).
Cancer patients are often dehydrated because they take in inadequate amountsof food and fluids and often suffer from nausea and vomiting. Dehydration reduces the ability of the kidneys to remove excess calcium from the body. Hormones and diuretics that increase the amount of fluid released by the body canalso trigger hypercalcemia.
Other conditions can cause hypercalcemia. Hyperparathyroidism, the excessivesecretion of parathyroid (the hormone that controls calcium levels) by one ormore of the parathyroid glands, is the most common cause of hypercalcemia inthe general population. Excessive intake of vitamin D can increase the intestinal absorption of calcium. During therapy for peptic ulcers, abnormally high amounts of calcium antacids are sometimes taken. Over use of antacids can cause milk-alkali syndrome and hypercalcemia. Diseases or conditions which cause bone loss or deterioration, such as Paget's and paralysis of the arms andlegs can also lead to hypercalcemia.
Severe hypercalcemia can be life-threatening. If the patient has normal kidney function, fluids can be given by vein (intravenously) to clear the excess calcium from the bloodstream. If the patient's kidneys are not working well, hemodialysis (a blood filtration therapy) is probably the safest and most effective method to reduce dangerous calcium levels.
Drugs such as furosemide, called loop diuretics, can be given after adequatefluid intake is established. These drugs inhibit calcium reabsorption in thekidneys and promote urine production. Drugs that inhibit bone loss, such as calcitonin, biphosphates, and plicamycin, are helpful in achieving long-term control. Phosphate pills help lower high calcium levels caused by a deficiencyin phosphate. Anti-inflammatory agents such as steroids are helpful with some cancers and toxic levels of vitamin D. Hyperparathyroidism is usually treated by surgical removal of one or more of the parathyroid glands.
Hypocalcemia, an insufficiency of serum calcium levels, can be causedby hypoparathyroidism, by kidney failure, by low levels of plasma magnesium (hypomagnesia), or by failure to get adequate amounts of calcium or vitamin Din the diet. Hypocalcemia may also result from the consumption of toxic levels of phosphate, found in certain enema formulas.
Symptoms of severe hypocalcemia include numbness or tingling around the mouthor in the feet and hands, as well as in muscle spasms in the face, feet, andhands. Hypocalcemia can also result in depression, memory loss, or hallucinations. Severe hypocalcemia occurs when free calcium in the bloodstream is under 3 milligrams per deciliter of blood. Chronic and moderate hypocalcemia canresult in cataracts. In this case, the term "chronic" means lasting one yearor longer.
Severe hypocalcemia requires injection of calcium ions (such as calcium gluconate). Long-term treatment of hypocalcemia includes oral calcium supplements(such as calcium carbonate, calcium chloride, calcium lactate, or calcium gluconate) and vitamin D supplements. Where hypocalcemia results from kidney failure, treatment includes injections of 1,25-dihydroxyvitamin D. If hypocalcemia is caused by low serum magnesium levels, the magnesium deficiency must becorrected to effectively treat the hypocalcemia.