Calcium homeostasis, normal conditions

For acute symptomatic hypocalcemia, 200 to 300 mg of elemental calcium is administered IV and repeated until symptoms are fully controlled. This is achieved by infusing 1 g of calcium chloride or 2 to 3 grams of calcium at a rate no faster than 30 to 60 mg of elemental calcium per minute. More rapid administration is associated with hypotension, bradycardia, or cardiac asystole. Total calcium concentration is commonly monitored in critically ill patients. Under normal circumstances, about half of calcium is loosely bound to serum proteins while the other half is free. Total calcium concentration measures bound and free calcium. Ionized calcium measures free calcium only. Under usual circumstances, a normal calcium level implies a normal free ionized calcium level. Ionized calcium should be obtained in patients with comorbid conditions that would lead to inconsistency between total calcium and free serum calcium (abnormal albumin, protein, or immunoglobulin concentrations). For chronic asymptomatic hypocalcemia, oral calcium supplements are given at doses of 2 to 4 g/day of elemental calcium. Many patients with calcium deficiency have concurrent vitamin D deficiency that must also be corrected in order to restore calcium homeostasis.2,37,38... 

Under normal conditions each of the two million nephrons of the kidney work in an organized approach to filter, reabsorb, and excrete various solutes and water. The kidney is a primary regulator of sodium and water as well as acid-base homeostasis. The kidney also produces hormones necessary for red blood cell synthesis and calcium homeostasis. Impairment of normal kidney function is often referred to as renal insufficiency. Based on the time course of development, renal insufficiency has historically been divided into two broad categories. Acute renal failure (ARF) refers to the rapid loss of renal function over days to weeks. Chronic kidney disease (CKD)", also called chronic renal insufficiency (CRI) by some, is defined as a progressive loss of function occurring over several months to years, and is characterized by the gradual replacement of normal kidney architecture with interstitial fibrosis. Progressive kidney disease or nephropathy is... 

The homeostasis of calcium in the blood is partly maintained by calcium excretion. Calcium is excreted in bile, urine, feces, and milk. Except during lactation, the kidney and intestine provide the main excretory paths for calcium. The exact amount of calcium that is excreted by way of the intestine is difficult to evaluate because of the large amounts of unabsorbed calcium normally present in the feces (6.5-8 mg/100 ml). Under normal conditions, it seems that little calcium is excreted through the intestine. The renal threshold for calcium is below the minimal levels of calciuni in the blood, so the glomeruli constantly remove calcium from the circulating blood. Most of the excreted calcium is reabsorbed in the tubules. In chronic renal failure, excessive amounts of calcium are lost in the urine, leading to decalcification of the bones and a form of secondary hyperparathyroidism. 

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