Dpd and Pyd are then excreted in free and peptide-bound forms into the urine. The free forms of the pyridinium crosslinks can be measured by immunoassay. While Pyd can be found in bone, cartilage, and many soft tissues, Dpd is located primarily in bone. Once diagnosed, patients can be treated with estrogen replacement therapy or antiresorptive medications. While DXA can also be used to accurately monitor therapy response, many months to years may be needed to detect measurable changes in bone density.
Biochemical markers are a valid alternative method for monitoring osteoporosis therapy.
Aurbach GD, et al. Metabolic bone disease. In Williams textbook of endocrinology , 8th ed. JD Wilson and DW Foster, eds. W.B. Saunders, Co., 1477-1517.