Physiologic regulation of the serum concentration of 1,25-dihydroxyvitamin D by phosphorus in normal men.

Abstract

We asked this question: in normal humans, is either a normal dietary intake or normal serum concentration of phosphorus a determinant of the serum concentration of 1,25(0H-)D? In seven normal men whose dietary phosphorus was decreased from 2,300 to 625 mg/d, each intake for 8-9 d, under strictly controlled, normal metabolic conditions, we measured serum concentrations of 1,25(OH)2D daily, and concentrations of phosphorus hourly throughout a 24-h period, before and after restriction. Decreasing dietary phosphorus induced: (a) a 58% increase in serum levels of 1,25(OH)2D; (b) a 35% decrease in serum levels of phosphorus measured in the afternoon; (c) a 12% decrease in the 24-h mean serum level of phosphorus; but, (d) no decrease in morning fasting levels of phosphorus. Serum concentrations of 1,25(OH)2D varied inversely and significantly with 24-h mean concentrations of phosphorus (r = -0.77, P < 0.001). When these data are combined with those of our prior study in which dietary phosphorus was varied over an extreme range, the relationship between serum levels of 1,25(OH)2D and 24-h mean serum levels of phosphorus is even stronger (r = -0.90, P < 0.001). In the aggregate, the results demonstrate that in normal men, dietary phosphorus throughout a normal range and beyond, can finely regulate the renal production and serum concentration of 1,25(OH)2D, and provide evidence that this regulation is mediated by fine modulation of the serum concentration of phosphorus.

Phosphate supplementation in young men: lack of effect on calcium homeostasis and bone turnover

“…There was no effect of phosphate on PTH in the second study. This was most likely due to the timing of the blood sampling, other studies have shown higher levels of serum phosphate and PTH after a meal (Calvo et al, 1990;Calvo et al, 1988;Portale et al, 1989). The dose of phosphate used in the second study was high, and was above the 2.5th percentile reported for British men of 2310 mgad (Gregory et al, 1990).…”

High phosphorus intake only slightly affects serum minerals, urinary pyridinium crosslinks and renal function in young women

“…Dietary phosphorus excess leads to reduced intestinal calcium absorption and 1,25-(OH) 2 D 3 production (Tanaka & Deluca, 1973;Portale et al, 1989;Rodriguez et al, 1991). Hyperphosphatemia, induced by a high-phosphorus diet in combination with low Ca intake, particularly common in women, is a major stimulus for PTH synthesis and secretion (Reiss et al, 1970;Prince et al, 1993;Nielsen et al, 1996).…”

Familial Hypophosphatemic Rickets - A Case Report and Review of Literature

“…So, the Ca ++ level in blood may remain within limit due to secondary hyperparathyroidism. This PTH also causes phosphates diuresis effect on kidneys lowering the serum phosphate 7 . But in this case, she has phosphaturia, not due to secondary hyperparathyroidism as PTH level was normal, as expected.…”

“…Familial hypophosphatemic or XLH rickets is one of the most common non-nutritional rickets, though it is less reported among paediatric group 7 . Generally, it is the late onset disease, not common in toddler group, like nutritional rickets 7 .…”

“…Generally, it is the late onset disease, not common in toddler group, like nutritional rickets 7 . However, it is more common among the growing age when he/she can bear weight.…”