Calcium and phosphorus metabolism during total parenteral nutrition

Calcium and phosphorus metabolism and balance were studied in 151 patients receiving total parenteral nutrition (TPN). Hypercalciuria was common, with mean (+/- SD) urinary calcium excretion 17.5 +/- 3.9 meq/24 hours (n = 2610). There was a significant positive correlation between urinary calcium excretion and parenteral calcium intake (r = 0.34, p less than 0.001). There was also a positive correlation between calcium balance and parenteral calcium intake (r = 0.61, p less than 0.001) in patients without extra-renal losses. Positive calcium balance was achieved with parenteral calcium intake greater than 15 meq/24 hours. Urinary phosphorus excretion correlated positively with parenteral phosphorus intake (r = 0.50, p less than 0.001). Phosphorous balance also correlated positively with parenteral phosphorus intake (r = 0.78, p less than 0.001). Positive phosphorus balance was achieved with parenteral phosphorus intake above 15 mmol/24 hours. Fifty-three patients received 1,000 IU vitamin D once weekly and showed no significant change in serum calcium. Ninety-eight patients received 1,000 IU vitamin D twice weekly and showed a gradual but significant mean increase over time in serum calcium.