Effect of phosphorus (P) supplementation in very low birthweight (VLBM) on calcium (Ca)

VLBW fed banked HBM are at risk from P depletion with hypercalciuria and high plasma 1.25 OHD concentration. The aim of this study was to deter mine the dose of P required to reduce urinary Ca (UCa) excretion. In addition, its effects on serum immunoreactive parathyroid hormon (iPTH) was also controlled. Forty two infants (GA = 27 - 34 W ; BW = 820 - 1350 g) were fed with HBM (up to 220 ml/kg/24 h) and given daily 1000 IU of vit-D2. 20 were randomly selected in control groups. P as K2 HPO4 was supplemented daily from the 28th day for 4 weeks : 0.48 mmol/kg in 11 infants (group I) and 0.8 mmol/kg in 11 infants (group II). In group I, there was no significant (sig.) change of serum Ca, P, iPTH and UCa (median & range) : 205 umol/kg/24 h (105 - 520) vs 286 (205 - 679) in controls. In group II a sig. increase in serum P and UP was observed with a sig. decrease in plasma 1.25 OHD 186 umol (106 - 271) vs 261 (213 - 293) and UCa 47 umol/kg/24 h (23 - 163) vs 332 (158 - 827) Serum Ca and plasma 25 OHD showed no sig. change. Serum iPTH increased slightly 55 ulEq/ml (< 25 - 80) vs 40 (< 25 - 50) but remained within the normal range (< 100).