Oral intake of phosphorus can determine the serum concentration of 1,25-dihydroxyvitamin D by determining its production rate in humans.

Abstract

Changes in the oral intake of phosphorus could induce the reported changes in the serum concentration of 1,25-dihydroxyvitamin D (1,25-(OH)2D) by inducing changes in its production rate (PR) or metabolic clearance rate (MCR), or both. To investigate these possibilities, we employed the constant infusion equilibrium technique to measure the PR and MCR of 1,25-(OH)2D in six healthy men in whom the oral intake of phosphorus was initially maintained at 1,500 mg/70 kg body weight per d for 9 d, then restricted to 500 mg/d (coupled with oral administration of aluminum hydroxide) for 10 d, and then supplemented to 3,000 mg/d for 10 d. With phosphorus restriction, the serum concentration of 1,25-(OH)2D increased by 80% from a mean of 38±3 to 68±6 pg/ml, P < 0.001; the PR increased from 1.8±0.2 to 3.8±0.6 tg/d, P < 0.005; the MCR did not change significantly. The fasting serum concentration of phosphorus decreased from 3.5±0.2 to 2.6±0.2 mg/dl, P < 0.01. With phosphorus supplementation, the serum concentration of 1,25-(OH)2D decreased abruptly, reaching a nadir within 2 to 4 d; after 10 d of supplementation, the mean concentration of 27±4 pg/ml was lower by 29%, P < 0.01, than the value measured when phosphorus intake was normal. The PR decreased to 1.3±0.2 jg/d, P < 0.05; the MCR did not change significantly.The fasting serum concentration of phosphorus increased significantly, but only initially. These data demonstrate that in healthy men, reductions and increases in the oral intake of phosphorus can induce rapidly occurring, large, inverse, and persisting changes in the serum concentration of 1,25-(OH)2D. Changes in the PR of 1,2540H)2D account entirely for the phosphorusinduced changes in serum concentration of this hormone.

Diurnal rhythm of plasma 1,25-dihydroxyvitamin D and vitamin D-binding protein in postmenopausal women: relationship to plasma parathyroid hormone and calcium and phosphate metabolism

“…High phosphate levels suppress and low levels increase the enzyme activity in accordance with our finding of an inverse relation between the two plasma compounds. In humans, phosphate restriction increases plasma 1,25(OH) 2 D by approximately 180% and phosphate supplementation decreases 1,25(OH) 2 D levels by 60% (23). However, in our study, total plasma 1,25(OH) 2 D as well as the free 1,25(OH) 2 D index showed a nadir in the morning with an increase in the day time during which regular meals were served.…”

Hyperphosphataemia Is Associated with the Diabetes-related Cardiovascular Risk Factors

“…The association of phosphorous with the risks of CVD has also been reported to involve vascular endothelial dysfunctions of the thoracic arterial rings and during direct incubation of endothelial cell culture with phosphorous 23 The mechanism through which the elevated phosphorous aggravates the CVD remains to be clarified, however, several correlates have been attributed: i high phosphorus levels appear to inhibit vitamin-D synthesis 24 ,…”

The Effects of Sevelamer Hydrochloride and Calcium Carbonate on Kidney Calcification in Uremic Rats

“…High serum P directly enhances parathyroid cell proliferation and PTH synthesis and secretion (6,7). High P also enhances parathyroid function indirectly by decreasing calcitriol synthesis and serum ionized Ca levels, which further elevates circulating PTH (27,28). High serum PTH induces osteitis fibrosa and bone loss, thus increasing serum Ca ϫ P product (29,30) and ectopic calcification (3,31).…”