Deoxypyridinoline (Dpd) is one of the two pyridinium cross-links that provide structural rigidity to type I collagen in bone. During osteoclastic resorption, Dpd is released into circulation and is excreted in the urine in free and peptide-bound forms.Deoxypyridinoline (Dpd) occurs mainly in Type I collagen of bone. After the formation of the Type I collagen matrix, the action of lysyl oxidase on two hydroxylysine and a lysine residue result in the formation of a Dpd cross link between two triple helical strands of collagen. Deoxypyridinoline (Dpd) has been described as a marker of bone turnover in metastatic breast cancer.Pyridinoline (PYD) and Deoxypyridinoline (DPD) are the major stable cross-links. These cross-links, primarily in bone and cartilage, have been found in all the connective tissues except the skin. PYD is the major component of these tissues, whereas DPD has only been detected in bone and dentine.
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