Abstract: Objective To analyze the relationship between the levels of melatonin(MT), advanced oxidized protein product(AOPP) and osteoporosis in elderly patients with chronic renal failure(CRF) undergoing maintenance hemodialysis.
Methods A total of 105 elderly patients with CRF undergoing maintenance hemodialysis in our hospital were enrolled. The incidence of osteoporosis was calculated, and the serum MT, AOPP levels and bone mineral density between osteoporosis patients and non-osteoporosis patients were compared. Pearson correlation analysis was performed on the relationship between serum MT and AOPP levels and bone mineral density in elderly patients with CRF undergoing maintenance hemodialysis. Logistic regression analysis was performed on the factors affecting osteoporosis in elderly patients with CRF undergoing maintenance hemodialysis. The receiver operating characteristic(ROC) curve was used to analyze the efficacy of serum MT and AOPP levels in predicting osteoporosis in elderly patients with CRF undergoing maintenance hemodialysis. 
Results The incidence of osteoporosis in patients with CRF undergoing maintenance hemodialysis was 45.71%. The serum AOPP level of osteoporosis patients was higher than that of non-osteoporosis patients(P＜0.05), and the serum MT level and bone density(lumbar spine L1-4 and bilateral femoral neck and Ward′s area) were lower than those of non-osteoporosis patients(P＜0.05). The results of Pearson correlation analysis showed that serum AOPP levels in elderly patients with CRF undergoing maintenance hemodialysis were negatively correlated with bone mineral density in different areas(P＜0.05), and serum MT levels were positively correlated with bone mineral density in different areas(P＜0.05). Compared with non-osteoporotic patients, the serum osteocalcin levels and dialysis age of osteoporosis patients had statistically significant differences(P＜0.05). Logistic multivariate regression analysis showed that serum dialysis age, AOPP, MT,and gender were independent risk factors for osteoporosis in elderly patients with CRF undergoing maintenance hemodialysis(P＜0.05). ROC analysis showed that the optimal cut-off points of MT and AOPP levels for predicting osteoporosis in elderly patients with CRF undergoing maintenance hemodialysis were 90.99 μmol/L and 21.66 ng/L respectively, and the area under the curve(AUC) was 0.859 and 0.713 respectively. 
Conclusion Elderly patients with CRF undergoing maintenance hemodialysis have abnormally increased serum AOPP levels, and abnormally decreased serum MT levels and bone mineral density. Serum AOPP and MT levels are correlated with bone mineral density in elderly patients with CRF undergoing maintenance hemodialysis, which can be used as sensitive indicators to predict osteoporosis in CRF patients. 

Key words: renal insufficiency, renal dialysis, melatonin