will therefore be retained in the plasma where they form insoluble salts with calcium ions, thereby removing them from the ionized calcium pool in the blood. the low levels of pth also inhibit the formation of calcitriol (not to be confused with calcitonin) from cholecalciferol (vitamin d3) by the kidneys. the reduction in the blood calcitriol concentration acts (comparatively slowly) on the epithelial cells (enterocytes) of the duodenum, inhibiting their ability to absorb calcium from the intestinal contents. the low calcitriol levels also act on bone causing the osteoclasts to release fewer calcium ions into the blood plasma. calcium homeostasis low plasma level when the plasma ionized calcium level is low or falls the opposite happens. calcitonin secretion is inhibited and pth secretion is stimulated, resulting in calcium being removed from bone to rapidly correct the plasma calcium level. the high plasma pth levels inhibit calcium loss via the urine while stimulating the excretion of phosphate ions via that route. they also stimulate the kidneys to manufacture calcitriol (a steroid hormone), which enhances the ability of the cells lining the gut to absorb calcium from the intestinal contents into the blood, by stimulating the production of calbindin in these cells. the pth stimulated production of calcitriol also causes calcium to be released from bone into the blood, by the release of rankl (a cytokine, or local hormone) from the osteoblasts which increases the bone resorptive activity by the osteoclasts. these are, however, relatively slow processes thus fast short term regulation of the plasma ionized calcium level primarily involves rapid movements of calcium into or out of the skeleton. long term regulation is achieved by regulating the amount of calcium absorbed from the gut or lost via the feces. disorders main article: disorders of calcium metabolism hypocalcemia (low blood calcium) and hypercalcemia (high blood calcium) are both serious medical disorders. osteoporosis, osteomalacia and rickets are bone disorders linked to calcium metabolism disorders and effects of vitamin d. renal osteodystrophy is a consequence of chronic kidney failure related to the calcium metabolism. a diet adequately rich in calcium may reduce calcium loss from bone with advancing (post-menopausal) age. a low dietary calcium intake may be a risk factor in the development of osteoporosis in later life; and a diet with sustained adequate amounts of calcium may reduce the risk of osteoporosis. research the role that calcium might have in reducing the rates of colorectal cancer has been the subject of many studies. however, given its modest efficacy, there is no current medical recommendation to use calcium for cancer reduction.