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PYRILINKS-D (deoxypyridinoline)

Bone is constantly undergoing a metabolic process called remodeling. This includes a degradation process, bone resorption mediated by the action of osteoclasts, and a building process, bone formation, mediated by the action of osteoblasts. Remodeling is required for the maintenance and overall bone health and resorption and formation are in balance. In abnormal states of bone metabolism and in some normal physiologic states such as menopause, this process becomes uncoupled and, when resorption exceeds formation, there is a net loss of bone. The measurement of specific degradation products of bone matrix provides analytical data of the rate of bone metabolism.

Pyrilinks-D

Approximately 90% of the organic matrix of bone is type I collagen, a triple helical protein. Type I collagen is crosslinked by specific molecules which provide rigidity and strength. Crosslinks of mature type I collagen are the pyridinium crosslinks, pyridinoline (Pyd) and deoxypyridinoline (Dpd). Dpd is formed by the enzymatic action of lysyl oxidase on the amino acid lysine. Dpd is released into the circulation during the bone resorption process. Dpd is excreted unmetabolized in urine and is unaffected by diet, making it suitable for assessing resorption. Pyrilinks-D is a urinary assay that provides a quantitative measure of the excretion of deoxypyridinoline crosslinks as an indicator of bone resorption.

Interpretation of Results

In the process of bone formation and breakdown, a bone specific product has been correlated with the rate of bone breakdown and preliminary evidence has suggested that the level correlates to the probability of osteoporotic fracture and response to hormone replacement.


Normal range for both female* and male
2.5 - 6.5 nM/mM Cr.

*Normal range determined in premenopausal, non pregnant women without bone or endocrine diseases.

CURRENTLY THIS TEST IS NO LONGER AVAILABLE.

Bone Health Assessment
The Bone Health Assessment measures N-Telopeptide and Creatinine in a urine sample. Unlike a bone mineral density scan which gives a static picture of bone loss, a pyrililnks test is capable of measuring active bone loss at the time of collection. Clinically, this means that patients can be monitored for osteoporosis treatment within weeks of onset (rather than waiting up to 2 years with the bone scan). Furthermore, patients at high risk of developing osteoporosis can determine if they are actively losing bone, before it shows up on bone scan. 

References

  1. Delmas PD: Biochemical markers for the assessment of bone turnover. Riggs BL, Melton LJ, III (eds): Osteoporosis: Etiology, Diagnosis, and Management. Philadelphia: Lippincott-Raven Publishers 1995:319-333
  2. Riggs BL: Overview of osteoporosis. West J Med 1991;154:63-77
  3. Robins Sp: Collagen Crosslinks in Metabolic Bone Disease. Acta Orthop Scand (Suppl 266) 1995;66:171-175
  4. Garnero P, Hausherr E, Chapuy M-C et al.: Markers of Bone Resorption Predict Hip Fracture in Elderly Women: The EPIDOS Prospective Study. J Bone Min Res 1996;11:1531-1538
  5. Hesley RP, Shepard KA, Jenkins DK et al.:Monitoring Estrogen Replacement Therapy and Identifying Rapid Bone Losers with an Immunoassay for Deoxypyridinoline. Osteoporosis Int 1998;8:159-164
  6. Seyedin SM, Rosen DM: Matrix Proteins of the skeleton. Curr Opin Cell Biol 1990;2:914-919
  7. Delmas PD, Gineyts E, Bertholin A, Garnero P, Marchand F: Immunoassay of pyridinoline crosslink excretion in normal adults and Paget's disease. J Bone Miner Res 1993;8:643-648
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