Kidneys parathyroid hormone affecting

Q7 Calcium is present in both intracellular fluid (ICF) and ECF, but the concentration in the ECF is twice as high as that in the ICF. Calcium is found in both ionized and bound forms, and Ca2+ homeostasis is mainly controlled by parathyroid hormone, which increases absorption of calcium in the intestine and reabsorption in the nephron. Calcitonin also affects ECF calcium concentration by promoting renal excretion when there is an excess of calcium in the body. The normal kidney filters and reabsorbs most of the filtered calcium however, in renal disease this is reduced and blood calcium decreases. Calcium and phosphate imbalance can occur in patients with renal failure, leading to osteomalacia (defective mineralization of bone). Osteomalacia is mainly due to reduced production of 1,25-dihydroxycholecalciferol, an active form of vitamin D metabolized in the kidney. Deficiency of 1,25-dihydroxycholecalciferol reduces the absorption of calcium salts by the intestine. 

The physiological role of vitamin D is to maintain calcium homeostasis. Phosphate metabolism is also affected. Vitamin D accomplishes its role by enhancing the absorption of calcium and phosphate from tte small intestines, promoting their mobilization from bone, and decreasing their excretion by the kidney. Also involved are parathyroid hormone and edeitonin. 

In addition to an increase in serum urea and creatinine levels, uric acid and inorganic phosphate levels also increase in chronic renal failure. The increase in serum inorganic phosphate leads to deposition of calcium phosphate in bones, causing hypocalcemia. In the early stages of chronic renal failure, calcium levels are restored by the stimulation of parathyroid hormone. However, as the renal disease progresses, the ability of the kidney to hydroxylate vitamin D and thus convert it to the active form decreases, thereby affecting the uptake of calcium by the gut and thus perpetuating hypocalcemia. Serum alkaline phosphatase levels increase due to disordered bone metabolism. Loss of bicarbonate is seen in some patients with increased parathyroid hormone activity. 

These two hormones, together with the vitamin calcitriol, regulate calciumhomeostasis and thereby indirectly affect phosphate metabolism. Parathyroid hormone (parathormone PTH) is secreted by the parathyroid glands as a polypeptide of 84 amino acid residues, and its action is to increase plasma calcium via parathyroid hormone receptors in bone, kidney, and a few other tissues. PTH secretion is increased in response to hypocalcemia and hyperphosphatemia conversely, increased plasma calcium suppresses PTH secretion. The renal production of 1,25-dihydroxycholecalciferol is also... 

The chemical form of aluminum affects aluminum absorption. Furthermore, the parathyroid hormones, vitamin D and iron seem to affect aluminum absorption."" In the human bloodstream aluminum is stored mainly in the Uver, kidneys, spleen, bones, and heart and brain tissues. 

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