Analysis Of Mineral Metabolism And Bone Turnover Markers And The Influencing Factors In Chronic Kidney Disease

Background and objective:CKD-MBD is defined as a systemic disorder of mineral and bone metabolism due to CKD that is manifested by one or a combination of the following:(I) abnormalities of calcium, phosphorous, PTH, or vitamin D metabolism;(2) abnormalities in bone histology; (3) vascular or other soft-tissue calcification. The mineral metabolism is the key of CKD-MBD, is also the basic cause of bone disease and vascular calcification. The skeleton is not only one of the tissues passively affected by the metabolic consequences of CKD, but also is the core of CKD-MBD. Bone biopsy is invasive and difficult to duplicate, so it need looking for possible biochemical markers of MBD to provide a basis for early diagnosis of CKD-MBD. Although KDIGO guidelines have been recommended for some of the indicators, the majority of clinical studies are still limited. In this cross section study, we objective to detect calcium, phosphorus, vitamin D changes and bone turn over markers and their influencing factors, and to lay a certain foundation for the diagnosis and treatment of MBD.Methods:This research is a cross-sectional study based on data obtained from chronic kidney disease patients who were admitted in PLA general hospital between March 2013 and May 2014.1) 204 patients who met the inclusion and exclusion criteria and have performed the 24-hour urine calcium (24UCE) and 24h phosphorus excretion (24hUPE) were included. All the patients were divided into 6 groups according to the renal function. Serum Ca, serum P and 24h urinary phosphorus excretion,24h urinary calcium excretion along with the change of renal function were observed; The influence factors of urinary excretion of calcium and phosphorus was analyzed; 2) Stage 2-5 CKD patients who met the inclusion and exclusion criteria were studied. Electrochemiluminescence immunoassay measured total 25-hydroxyvitamin D. According to the renal function, the change and influencing factors of 25 (OH) D were observed;3)263 patients who have performed PINP、β-CTX、OC test were selected.The changes of these three markers of bone turnover were observed and studied.Results:1) 204 patients who have completed 24hUCE and 24hUPE were divided into 6 groups(CKD1,CKD 2.CKD3a. CKD 3b. CKD 4, CKD 5) according to renal function. There were significant differences in the levels of serum Ca, P,24hUCE and 24h UPE. Draw the curve of Serum Ca. Serum P,24h UCE,24h UPE, and we found 24h UCE decreased gradually with the decline in renal function. Serum calcium <2.25mmol/L in eGFR<40ml/min/1.73m. Divided all patients into 2 groups (male, female), we found that male urinary calcium excretion is higher than female (1.65±1.62 vs 1.01±1.00, P=0.00). Analying postmenopausal women and the corresponding age of men, we found body weight corrected 24hUCE,24hUPE were not statistically significant difference; Multivariate linear regression analysis revealed that 24h UCE and 24hUPE could be affected by gender.2) 207 stage 2-5 CKD patients were included in this study, of which 40.1% were women, and 25 (OH) D levels greater than 15 ng/ml were accounted for 20.3% of the patients.25 (OH) D decreased with the decline of renal function gradually; Multivariable linear regression analysis showed that 25(OH) D concentration is associated with 24h urinary protein (B=-1.54, P= 0.00) and serum calcium (B=5.07, P= 0.04); 3) PINP,β-CTX and osteocalcin were detected in 263 patients according to renal function analysis. With the decrease of renal function, PINP, P-CTX and osteocalcin levels were significantly increased; Urinary PINP, β-CTX were detected in 69 patients, and the levels of these marker increased with decrease of renal function. Linear regression analysis showed that the relation of OC and PINP, β-CTX, and PINP and β-CTX correlation also existed.Conclusions:The concentration of serum Ca and P change in advanced CKD; 24h UPE and 24h UCE reduce with the renal function declines. Gender plays an important role in the excretion of urine calcium and phosphorus. Vitamin D deficiency is common in CKD patients. Proteinuria is important reason for the lack of vitamin D. With the decline in renal function, serum osteocalcin, serum PINP, CTX, OC increase gradually.