[Importance of biochemical indicators of bone turnover in patients on chronic dialysis and after kidney transplantation].
Bone remodeling is a continuous process of removal of microscopic amounts of bone tissue due to synchronized actions of osteoclasts and osteoblasts with the purpose of renewal and repair of bone tissue. During the formation of bone matrix osteoblasts synthesize proteins. Measurement some of these proteins in blood has clinical significance as indicators of bone formation: osteocalcin, procollagen type I propeptide, and bone alkaline phosphatase. During osteoclastic bone resorption, collagen type I breakdown fragments are released in the circulation and excreted in the urine, and measured in serum or urine as bone resorption markers (telopeptide, pyridynolines). Bone metabolism and accordingly bone markers are subjected to considerable biologic variation. The effects of age, sex, race, pregnancy and lactation, fracture, disease and certain drugs cannot be avoided and must thus be considered when interpreting the results. Circadian variation is excluded by obtaining samples in the morning and the effect of exercise prevented. The use of bone markers has been extensively studied in monitoring the effect of antiresorptive treatment in osteoporotic women. A decrease of 30-50% occurs within 3 months after the beginning of hormone replacement therapy or bisphosphonates and remains at this level. In patients on chronic dialysis treatment, bone markers are increased and reflect bone metabolism as assessed by bone biopsy. Although bone markers enable discrimination between high and low bone turnover, they cannot substitute for bone biopsy in determination of the type of renal osteodystrophy. The factors affecting bone disorder in these patients, i.e. dialysis duration or parathyroid function correlate with bone markers. In kidney transplant recipients, an increased bone turnover and its normalization after approximately 2 years can be assessed by bone markers. Similar to chronic dialysis, risk factors for bone disorder after kidney transplantation (e.g., dialysis duration, parathyroid function, age, sex, immunosuppressants, corticosteroids, graft function) are associated with bone markers. We present cross-sectional and longitudinal data on 100 patients on chronic dialysis and 80 kidney transplant recipients. In conclusion, sufficient evidence exists indicating that the measurement of bone markers enables assessment of bone turnover and its dynamics. However, no guidelines or recommendations have been put forward to validate their use in routine clinical practice of chronic dialysis or kidney transplantation bone disorders.
Kusec
Vesna
V
Klinicki zavod za laboratorijsku dijagnostiku, Centar za dijalizu, Klinicki bolnicki centar Zagreb, Zagreb, Hrvatska. vkusec@kbc-zagreb.hr
Smalcelj
Ruzica
R
D000469:Alkaline Phosphatase / Q000097:blood; D015415:Biomarkers / Q000097:blood; D001862:Bone Resorption / Q000175:diagnosis* / Q000209:etiology; D012080:Chronic Kidney Disease-Mineral and Bone Disorder / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D016030:Kidney Transplantation / Q000009:adverse effects*; D015675:Osteocalcin / Q000097:blood; D010446:Peptide Fragments / Q000097:blood; D011347:Procollagen / Q000097:blood; D006435:Renal Dialysis / Q000009:adverse effects*
D015415:Biomarkers; D010446:Peptide Fragments; D011347:Procollagen; C042813:procollagen type I carboxy terminal peptide; D015675:Osteocalcin; D000469:Alkaline Phosphatase