EFFECT OF SALMON-CALCITONIN ON DEOXYPYRIDINOLINE (DPYR) URINARY-EXCRETION IN HEALTHY-VOLUNTEERS

To evaluate the influence of synthetic salmon calcitonin (SMC) on bone resorption we investigated the modifications in urinary cross-links excretion [pyridinoline (Pyr) and deoxypyridinoline (Dpyr)] induced by a single dose of the drug. The study was carried out in 16 healthy volunteers given a single dose of either 50 IU SMC I.M. or placebo, according to a double-blind, cross-over design. Urine was collected every 24 hours during the 72 hours after each treatment and Pyr and Dpyr were measured by an automated HPLC method. Pyr showed no significant difference after the two treatments, whereas in the first 24-hour urine collection Dpyr (nmol/24 hours +/- SD) was considerably lower after SMC than after placebo (118.9 +/- 26.0 against 147.2 +/- 45.0, P < 0.05). The amount of saved Dpyr was 19.2%. The selective effect of SMC on Dpyr excretion was more evident comparing the Pyr/Dpyr ratios for placebo and SMC during the first day of the study (4.1 +/- 0.6 against 4.8 +/- 0.7, respectively, P < 0.01). Using Eyre's formula (10 nmol Dpyr = 0.17 g bone) and assuming that no Dpyr is metabolized, the mean daily amount of bone resorbed was calculated (2.5 g for placebo and 2.0 g for SMC). The difference is the index of the bone-saving effect of SMC (0.48 g/day, or 19.2%). In conclusion, assuming that in healthy volunteers bone turnover is balanced with equal rates of formation and resorption, a dose of 50 IU I.M. of SMC reduces resorption, with a bone gain in the first 24 hours calculated as 9.4 mg/IU.