Endocrine Abstracts

Measurement of the various available bone formation and resorption markers provide insights into different aspects of the bone metabolism process. Interpretation of bone biomarkers in a clinical setting is complex. Analysis of formation markers including bone alkaline phosphatase, procollagen type 1 propeptide and intact osteocalcin and resorption markers including free deoxypyridinoline and N-terminal cross-linking telopeptide of type 1 collagen were performed. From the interpretation of these analyses we propose indices of bone remodelling balance (BRBI) and turnover (BTI) using intact osteocalcin (OCI), a marker of bone formation and N-telopeptide of type I collagen (NTx), an indicator of bone resorption. T values, the number of standard deviations a patient's bone analysis is below or above the mean of a young normal reference population were used to derive the indices. BRBI = formation biomarker - resorption biomarker and BTI = formation + resorption biomarker. T values for patients with Paget's disease (n=17), osteoporosis (n=13) and active primary hyperparathyroidism (n=7) were compared with controls (n=16 men and n=17 women). OCI - NTx provided the optimum BRBI and OCI + NTx provided the optimum BTI reflecting current concepts of bone metabolism in normal and disease states.

Results are expressed as mean±SEM.

In Paget's disease the BRBI pre treatment(-21.3±8.583)versus controls (-0.078±0.121) p<0.001 indicate significant net bone loss suppressed by treatment (0.044± 1.236). The BTI in Paget's disease pre treatment (35.10±8.77) versus controls (-0.166±0.309) p<0.001 indicate high turnover which returns to normal after treatment(2.116 ±4.78).

For osteoporosis pre treatment,the indices point towards negative remodelling balance(-1.025±0.553)without abnormal turnover(0.494±1.186)which is suppressed during treatment(-2.986±0.427).

The indices demonstrate that primary hyperparathyroidism is associated with high turnover (5.333±2.125) and net bone gain (2.121±0.813) both of which are significantly different from controls p<0.001.

These observations suggest BRBI and BTI hold promise in the interpretation of bone biomarkers thus facilitating our understanding and management of metabolic bone disease.