An average daily dietary calcium intake is in the range of 600 to 900 mg. Approximately one third of that, 300 to 350 mg, is absorbed in the small intestine. Because half of the calcium absorbed in the small intestine, 150 to 200 mg, is then secreted by the colon, the net uptake from the gastrointestinal tract is in the range of 150 to 200 mg per day. Normally, calcium in the bones is in equilibrium with the body pool and there is no net gain or loss of calcium from the skeleton. Thus, the net gastrointestinal calcium absorption is balanced by urinary calcium excretion of 150 to 200 mg per day.
KeywordsProximal Tubule Calcium Transport Electrochemical Gradient Urinary Calcium Excretion Proximal Convoluted Tubule
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