Effect of Phosphate Supplementation to Breast Fed Very Low Birthweight Infants on Urinary Calcium Excretion, Serum Immunoreactive Parathyroid Hormon and Plasma 1.25-Dihydroxy-vitamin D Concentration

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Abstract
The effect of two doses of Phosphorus (P) supplementation to pooled breast milk (BM): 0.48 and 0.800 mmol/kg/24 h given during the second month of life was evaluated in 22 very low birthweight [human] infants. The concentration of calcium and phosphorus in serum and urine, the serum concentration of immunoreactive parathyroid hormon (iPTH) and the plasma 1,25-dihydroxy-vitamin D concentration (1,25-OH-D) were compared to the values in 19 control infants. The mean .+-. SD concentrations in control infants and adults are 63 .+-. 18 .mu.lEq/ml for serum iPTH and 85 .+-. pmol/l for plasma 1,25-OH-D. With 0.48 P supplementation, urinary Ca (UCa) excretion (median and range) 0.238 mmol/kg/24 h (0.105-0.520) was lower than in the control group 0.288 (0.205-0.679) (p < 0.05); the reduction of UCa was larger with 0.8 P supplementation: 0.047 (0.023-0.163) (p < 0.01). P supplementation induced no change in serum Ca concentration but a slight and significant increase in serum iPTH was observed only with the 0.8 P supplementation: 55 .mu.l Eq/ml (<25-80) (p < 0.05). with 0.8 P supplementation there was no significant change of plasma 1,25-OH-D concentration: 173 pmol/l (106-271) vs. 255 (132-293) in the control group. These data show that with 0.8 P supplementation, the hypercalciuria in BM-fed infant disappears without secondary hyperparathyroidism, but without any change in plasma 1,25-OH-D concentration.