SHORT-TERM MODIFICATIONS INDUCED BY HIGH DOSIS OF CALCITRIOL ON SERUMBONE MARKERS IN CHRONIC-HEMODIALYSIS PATIENTS

Thirteen patients (7 males) were selected (58 +/- 14 years old and 62 +/- 71 months in dialysis) without calcitriol treatment in the last si x months. We performed the lest on a dialysis free day to minimize the effects of dialysis on parathyroid function. After a fast of 10 hours , we administered an infusion of 2 mu g of calcitriol and then determi ned PTHi, osteocalcin (OC), type I collagen-telopeptide (ICTP) and tar trate-resistant acid-phosphatase (TRAP) serum levels at 0, 3, 6 and 24 hours following the calcitriol bolus. PTHi levels only decreased sign ificantly al 24 hours (520 +/- 436 vs 360 +/- 270 pg/ml, 22 +/- 23%, p < 0.05) the fall varying widely from one patient to another (7-69%). This decline in PTHi did not correlate with the degree of secondary hy perparathyroidism. OC levels increased slightly but without statistica l significance (37,4 +/- 24 vs 45 +/- 29 ng/ml). ICTP did not change, while TRAP rose mildly at 24 hours (7.4 +/- 1.8 vs 7.8 +/- 8 Ul/ml, p < 0.05). Serum phosphorus levels decreased at 3-6 hours and rose again significantly at 24 hours. We did not observe changes in serum calciu m levels. PTHi correlated with OC and TRAP serum levels whereas ICTP d id not. In conclusion, PTHi production in haemodialysis patients can b e inhibited by calcitriol as early as 24 hours after its administratio n as an intravenous bolus, without accompanying changes in serum calci um levels. OC can be rise in some patients after 24 hours of calcitrio l infusion. Other bone markers such as ICTP or TRAP do not show import ant short-term modifications with calcitriol.