ASSESSMENT OF DIFFERENT MARKERS OF BONE-RESORPTION IN POSTMENOPAUSAL OSTEOPOROTIC WOMEN TREATED WITH PAMIDRONATE

The aim of this study was to evaluate the different bone resorption ma rkers, total pyridinoline (Pyr) and total deoxypyridinoline (Dpyr), as sessed by a HPLC method, free Dpyr, assessed by a new immunoassay, and urinary excretion of hydroxyproline (OH-proline), in postmenopausal o steoporotic women during long-term treatment with pamidronate. A total of 60 postmenopausal women with previous distal forearm fracture were included in this 12-month placebo-controlled and double-blind study, where intermittent oral pamidronate, 75 or 150 mg, or placebo were giv en daily for 4 weeks, every 16 weeks. After 1 week a significant reduc tion in urinary excretion of total Dpyr was observed in the group trea ted with 150 mg pamidronate compared to the placebo (p<0.01) and to th e 75-mg group (p<0.001). A maximal 50.4% decrease in total Dpyr, (p<0. 0001 compared to the placebo group, p<0.01 compared to the 75-mg group ), was observed after 3 weeks of treatment with 150 mg pamidronate, an d this decrease persisted to week 52. After 4 weeks of treatment with 150 mg pamidronate the maximal decrease in free Dpyr was only 26.5%, w hich persisted during 12 months of treatment. Decreases in urinary exc retion of total PYr and OH-proline were less than the decreases in tot al Dpyr The correlation between total Dpyr (HPLC method) and free Dpyr (Pyrilinks-D assay) at baseline was r=0.91. Total Dpyr assessed by th e HPLC method reflects the pamidronate-induced decrease in bone resorp tion, and the changes in this resorption marker were more pronounced t han changes in free Dpyr, total Pyr and OH-proline. In this study free Dpyr analysis was less suitable for reflecting bone resorption during bisphosphonate therapy.