Endocrine Abstracts

The diagnostic possibilities of using biochemical markers of bone metabolism in patients with secondary hyperparathyroidism (SHPT) and chronic kidney disease (CKD) have not yet been adequately evaluated. The aim of the study: To evaluate biochemical markers of bone metabolism in patients with various stages of CKD, their relationship with SHPT and bone mineral density.

Materials and Methods: The study included 452 patients with various stages of CKD and 60 persons of the comparison group without CKD aged 20 to 70 years. Serum levels of parathyroid hormone (PTH), vitamin D (25(OH)D), calcium (Ca), phosphorus (P), alkaline phosphatase (AP), osteocalcin (OC), collagen type 1 crosslinked C-telopeptide (CTX) were determined by enzyme immunoassay. Bone mineral density of the lumbar spine (LS), proximal femurs (PF), femoral necks (FN), radius (R), distal part of the radius (R33%) was assessed by double X-ray absorptiometry (DXA). A neural network algorithm for clustering patients was applied to identify a cluster of patients with optimal bone tissue parameters.

Results: The incidence of osteoporosis in patients with CKD ranged from 13.8% in LS, PF, FN to 28.2% in radius. Incidence of osteoporosis increased up to 20% in patients with CKD 4-5. PTH is a major factor of BMD loss in CKD patients, maximum frequency of osteoporosis was noted in patients with SHPT and CKD5. A significant relationship was established between the OC, CTX, ALP and PTH, as well as with the presence of osteoporosis. OC, CTX, ALP progressively increase with exacerbation of renal failure, which is a consequence of a violation of both bone metabolism and degradation and elimination in conditions of reduced renal function. Population-wide reference intervals OC, CTX are not applicable in patients with CKD 4-5. Using a neural network algorithm, we proposed reference intervals for osteocalcin: CKD 4 - 55-125 pg/ml, CKD 5 before dialysis - 35-235 pg/ml, dialysis - 70-550 pg/ml; for CTX: CKD 4 - 0.3-1.2 pg/ml, CKD 5 before dialysis - 0.7-2.3 pg/ml, dialysis - 0.7-2.5 pg/ml.

Conclusion: The detection of low BMD in patients with SHPT and CKD in some cases requires clarification of bone metabolism. Estimation of OC, CTX, ALP can be used for such purpose. When interpreting the results of the assessment of OC, CTX, the specific reference intervals in CKD 4-5 should be taken into account.