Urinary collagen crosslinks reflect further bone loss of femoral neck in osteoporotic patients undergoing vitamin D therapy.

Bone mineral density (BMD) of the lumbar (L2-LA) spine and femoral neck was measured annually for 2 years (3 times beginning at the beginning of year 1 and after each subsequent year) in 39 female patients with osteoporosis undergoing 0.5 or 1.0 microg daily doses of vitamin D therapy. At the time of the first BMD measurement, biochemical markers including serum alkaline phosphatase (ALP), urinary pyridinoline (Pyr), deoxypyridinoline (Dpyr) and hydroxyproline (Hyp) were also measured. Urinary Pyr and Dpyr correlated with the percent changes of femoral neck BMD measurements taken the year following the sampling (Pyr: r=-0.622, p<0.001, Dpyr: r=-0.385, p<0.05). Only urinary Pyr correlated with the percent changes of femoral neck BMD measurements taken the following 2 years (r=-0.532, p<0.05). Neither serum ALP nor urinary Hyp correlated with the percent changes of spine or femoral neck BMD measurements taken the year or 2 years after the sera and urine sampling. In summary, we believe urinary Pyr and Dpyr can reflect subsequent bone loss of the femoral neck BMD having been measured only once during the course of a year.