Serum calcium measurement is used to diagnose and monitor a wide range of disorders, including bone, kidney, parathyroid, and gastrointestinal diseases. Blood calcium levels can also be used to assess vitamin D and albumin levels in the body.
Calcium (Ca) is found in the blood in two forms. About 50% is in free form and the other 50% is bound to plasma proteins, mainly albumin. The free-circulating calcium is biologically active. Its functions include muscle contraction, heart function, the transmission of nerve signals, and blood clotting. The amount of calcium in the blood is minimal compared to 98% to 99% stored in the teeth and bones. Bone storage provides an excellent reservoir that is readily available for release into the bloodstream, maintaining a normal blood calcium level. There is an inverse relationship between calcium and phosphorus: when the concentration of calcium in the serum increases, the concentration of phosphorus decreases.
Two hormones work together to control blood calcium levels. Calcitonin (CT), which is secreted by the thyroid gland and causes kidney calcium excretion, results in a decrease in blood calcium and parathyroid hormone (PTH) which directly acts to the bones in order to release calcium in the blood when needed and also increases the absorption of calcium from the intestine and kidneys.
Blood calcium measurement provides important information on the function of the parathyroid glands and the metabolism of calcium. It is also used for the evaluation of certain neoplasms, since the cancer cells release calcium, resulting in high levels of calcium in the blood (hypercalcemia).
Since much of the circulating calcium is linked to albumin, blood calcium levels must be interpreted in relation to albumin concentration. When albumin is reduced by 1 g, the total serum calcium concentration is reduced by about 0.8 mg due to a decrease in bound calcium. The amount of free calcium does not change. Patients with hypercalcemia may have deep bone pain, nephrolithiasis, and muscle weakness. Patients with hypocalcemia or reduced serum calcium may experience numbness and tingling in the hands, feet, and around the mouth, muscle contractions, cardiac arrhythmias, and possibly convulsions. These patients may also present with Chvostek and Trousseau.
What Do Pathological Values Mean?
- Increase: Acromegaly, Addison's disease, antacid abuse, dehydration, Hodgkin's disease, hyperparathyroidism, hyperthyroidism, prolonged immobilization, leukemia, lung cancer, metastatic bone cancer, parathyroid carcinoma, pancreatic cancer, sarcoidosis, vitamin D poisoning, Williams syndrome. Medications: anabolic steroids, androgens, antacids, calcium carbonate, calcium gluconate, calcium salts, ergocalciferol, estrogen, hydralazine, indomethacin, lithium, parathyroid hormone, progesterone, tamoxifen, theophylline, thiazide diuretics, thyroid hormones, vitamin A, vitamin D.
- Decrease: Acute pancreatitis, alcoholism, chronic kidney disease, diarrhea, early neonatal hypocalcemia, hyperphosphatemia, hypoparathyroidism, low albumin level, malabsorption, massive blood transfusions, metabolic alkalosis, osteomalacia, renal failure, rickets, severe malnutrition, vitamin D deficiency. Medications: acetazolamide, antacids, anticonvulsants, asparaginase, aspirin, barbiturates, calcitonin, cisplatin, corticosteroids, cholestyramine, furosemide, gastrin, gentamicin, glucagon, glucose, heparin, hydrocortisone, insulin, iron, laxatives, loop diuretics, magnesium salts, methicillin, phenobarbital, phenytoin, sulfonamides.
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
