CALCIUM AND VITAMIN-D HOMEOSTASIS IN PATIENTS WITH HEAVY PROTEINURIA

In the present study calcium and vitamin D metabolism was studied in f ifty patients with daily urinary protein excretion exceeding 3 g/24 ho urs. A positive correlation was seen between serum albumin and ionized calcium concentration (r=0.51, p<0.001). All patients with normal ren al function had their intact PTH within normal range, though seven of these 16 had serum ionized calcium below the lower margin of the refer ence range. The mean serum albumin was significantly lower in the seve n patients with low serum ionized calcium when compared with those wit h serum ionized calcium above the lower normal margin (19 g/l vs. 30 g /l, respectively, p<0.001), but there was no difference in plasma inta ct PTH (3.7+/-1.3 pmol/l vs. 3.1+/-0.7 pmol/l, p = 0.21, ns.). Serum 2 5OHD(3) correlated negatively with the degree of proteinuria (r = -0.5 0, p <0.001) and positively with serum albumin (r = 0.66, p <0.001). S erum 1,25(OH)(2)D-3 was related to serum 25OHD(3) (r = 0.39, p <0.01), but its association with serum phosphate, PTH, the degree of proteinu ria and renal function did not reach statistical significance. In conc lusion, a significant correlation between serum ionized calcium and al bumin was observed, and in hypoalbuminemia hypocalcemia did not induce PTH response of expected magnitude. In patients with marked hypoalbum inemia a low measured ionized calcium does not have the same clinical impact as it would have in normalbuminemia and it has to be interprete d cautiously. Secondly, abnormal regulation of 1,25(OH)(2)D-3, and in particular its dependency on 25OHD(3), was observed in patients with h eavy proteinuria.