Calcium

: A mineral found mainly in the hard part of bones. Bones serve as a storage area for calcium. Calcium is added to bones by cells called osteoblasts. It is removed from bones by cells called osteoclasts. When children consume calcium, they absorb 75% of it into their bones. By the age of 20, the absorption drops to 30 to 50% and calcium is no longer used to build but to maintain bone density, to replace the calcium lost as the bones constantly remodel themselves. Calcium is not just essential for healthy bones. It is also important for muscle contraction, heart action, nervous system maintenance, vitamin B-12 absorption and normal blood clotting. A low blood calcium (hypocalcemia) makes the nervous system highly irritable with tetany (spasms of the hands and feet, muscle cramps, abdominal cramps, overly active reflexes, etc.). Chronic calcium deficiency contributes to poor mineralization of bones, soft bones (osteomalacia) and osteoporosis; and, in children, rickets and impaired growth. Overly high intake of calcium (hypercalcemia) may cause muscle weakness and constipation, affect the conduction of electrical impulses in the heart (heart block) lead to calcium stones (nephrocalcinosis) in the urinary tract, impair kidney function, and interfere with the absorption of iron, predisposing to iron deficiency. Food sources of calcium include dairy foods, some leafy green vegetables such as broccoli and collards, canned salmon, clams, oysters, calcium-fortified foods, and tofu. Milk packs a fairly high dose of calcium: 300 milligrams in an eight-ounce glass. According to the National Academy of Sciences, adequate intake of calcium is 1,200 milligrams a day (four glasses of milk) for men and women 51 and older, 1,000 milligrams a day for adults 19 through 50, and 1,300 milligrams a day for children 9 through 18. The upper limit for calcium intake is 2.5 grams daily.

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A metallic bivalent element; atomic no. 20, atomic wt. 40.078, density 1.55, melting point 842°C. The oxide of c. is an alkaline earth, CaO, quicklime, which on the addition of water becomes c. hydrate, Ca(OH)₂, slaked lime. For some organic c. salts not listed below, see the name of the organic acid portion. Many c. salts have crucial uses in metabolism and in medicine. C. salts are responsible for the radiopacity of bone, calcified cartilage, and arteriosclerotic plaques in arteries. [Mod. L. fr. L. calx, lime]

- c. alginate a topical hemostatic.

- c. aminosalicylate the c. salt of p-aminosalicylic acid, with the same uses.

- c. benzoylpas an antituberculous agent.

- c. bromide used to meet the same indications as potassium bromide.

- c. carbide blackish crystalline lumps that when in contact with water yield acetylene gas.

- c. carbimide a fertilizer and weed seed killer that also exhibits antithyroid activity; like disulfiram, it impairs ethanol metabolism; workers in cyanamide-producing plants exhibit systemic symptoms (“Monday-morning illness”) after ingestion of alcohol. SYN: c. cyanamide.

- c. carbonate an astringent, antacid, and c. dietary supplement. SEE ALSO: calcite. SYN: chalk, creta.

- c. caseinate the form of casein present in cow's milk; used in dietetic preparations; has been used for diarrhea in infants.

- c. chloride used to correct c. deficiencies and in the treatment of magnesium intoxication and cardiac failure.

- citrated c. carbimide a mixture of two parts citric acid to one part c. carbimide; in the metabolism of ethanol, it slows the conversion of acetaldehyde to acetate; used in the treatment of alcoholism.

- crude c. sulfide used externally in the treatment of acne, scabies, and ringworm. SYN: sulfurated lime.

- c. cyanamide SYN: c. carbimide.

- dibasic c. phosphate used as a c. and phosphorus dietary supplement. SYN: c. monohydrogen phosphate, secondary c. phosphate.

- c. folinate SYN: leucovorin c..

- c. glubionate a c. replenisher.

- c. gluceptate used as a nutrient. SYN: c. glucoheptonate.

- c. glucoheptonate SYN: c. gluceptate.

- c. gluconate a salt of c. more palatable than the chloride, sometimes used as a c. supplement.

- c. glycerophosphate a c. and phosphorus dietary supplement.

- c. hippurate said to be a solvent of uratic gravel and calculi.

- c. hydroxide used as a carbon dioxide absorbent.

- c. hypophosphite has been used for rickets and impaired nutrition.

- c. iodate used as a dusting powder and, in lotion and ointment, as an antiseptic and deodorant.

- c. iodobehenate a c. salt, (C₂₁H₄₂ICOO)₂Ca, formerly used to meet the indications of the ordinary iodides.

- c. ipodate a radiopaque medium used in cholangiography and cholecystography.

- c. lactate used as a c. replenisher.

- c. lactophosphate a mixture of c. lactate, c. acid lactate, and c. acid phosphate; used as a c. and phosphorus dietary supplement.

- c. leucovorin leucovorin c..

- c. levulinate a hydrated c. salt of levulinic acid; it has the usual effects of c. administered orally or intravenously.

- c. mandelate c. salt of mandelic acid; a urinary anti-infective agent.

- milk of c. densely calcified fluid, most often found radiographically in the gallbladder in association with chronic obstruction.

- c. monohydrogen phosphate SYN: dibasic c. phosphate.

- c. oxalate found as sediment in the urine and in urinary calculi. Toxic end product of ethylene glycol consumption.

- c. oxide SYN: lime (1).

- c. pantothenate the c. salt of pantothenic acid; a vitamin B filtrate factor.

- precipitated c. carbonate used as an antacid in the management of peptic ulcers and other conditions of gastric hyperacidity.

- c. propionate the c. salt of propionic acid; an antifungal agent.

- racemic c. pantothenate a mixture of the c. salts of the dextrorotatory and levorotatory isomers of pantothenic acid; same uses as c. pantothenate.

- c. saccharate used as an antacid in dyspepsia and flatulence, as an antidote in carbolic acid poisoning, and as a stabilizer for c. gluconate solution for parenteral administration.

- secondary c. phosphate SYN: dibasic c. phosphate.

- c. stearate a soap used in the preparation of tablets as a lubricant for tablet machinery and to keep powder mixtures flowing.

- c. sulfate CaO₄S; used in exsiccated form to make plaster of Paris. SEE ALSO: gypsum.

- c. sulfite used as an intestinal antiseptic, and locally in the treatment of parasitic skin diseases.

- tertiary c. phosphate SYN: tribasic c. phosphate.

- tribasic c. phosphate used as an antacid. SYN: bone ash, bone phosphate, tertiary c. phosphate, tricalcium phosphate, whitlockite.

- c. trisodium pentetate SYN: pentetate trisodium c..

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cal·ci·um 'kal-sē-əm n, often attrib a silver-white bivalent metallic element that is an alkaline earth metal, occurs only in combination, and is an essential constituent of most plants and animals symbol Ca see ELEMENT (table)

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n.

a metallic element essential for the normal development and functioning of the body. Calcium is an important constituent of bones and teeth: the matrix of bone, consisting principally of calcium phosphate, accounts for about 99% of the body's calcium. It is present in the blood at a concentration of about 10 mg/100 ml, being maintained at this level by hormones (see calcitonin, parathyroid hormone). It is essential for many metabolic processes, including nerve function, muscle contraction, and blood clotting.

The normal dietary requirement of calcium is about 1 g per day: dairy products (milk and cheese) are the principal sources. Its uptake by the body is facilitated by vitamin D; a deficiency of this vitamin may therefore result in such conditions as rickets, osteoporosis, and osteomalacia. A deficiency of calcium in the blood may lead to tetany. Excess calcium may be deposited in the body as calculus (stones), especially in the gall bladder and kidney. Symbol: Ca.

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cal·ci·um (Ca) (kalґse-əm) [L. calx lime] a silvery yellow metal, the basic element of lime. Atomic number, 20; atomic weight, 40.08. It is found in nearly all organized tissues, being the most abundant mineral in the body. In combination with phosphorus it forms calcium phosphate, the dense, hard material of the teeth and bones. It is an essential dietary element, a constant blood calcium level being essential for the maintenance of the normal heartbeat, and for the normal functioning of nerves and muscles. It also plays a role in multiple phases of blood coagulation (in which it is called coagulation factor IV) and in many enzymatic processes.