Endocrine Abstracts

While it is generally acknowledged that hyperthyroidism and Paget's disease are states of increased bone turnover and that treatment reduces this, whether treatment entirely corrects or reverses abnormalities has not been established. A variety of biomarkers for bone formation which include serum levels of bone alkaline phosphatase (BAP), osteocalcin (OC) and amino terminal procollagen type 1N propeptide (PINP) and resorption biomarkers which include urinary excretion of deoxypyridinium crosslinks (DPD) and N-telopeptide of type 1 collagen (NTX) are available. Difficulty in interpretation of individual bone biomarkers has led us to devise indices of bone turnover (BTI) and bone remodelling balance (BRBI) based on the sum or difference between a formation marker and a resorption marker expressed in T values. We measured BTI and BRBI in a cohort of hyperthyroid (n=8) and Paget's disease (n=8) patients pre and post appropriate treatment. In Paget's disease the BRBI (BAP-NTX) fell from 4.3±4.87 to 0.89±1.15 (p<0.05) while BTI (BAP+NTX) fell from 25.8±8.09 to 0.14±1.12, (p<0.01). In the hyperthyroid group, BRBI (PINP-DPD) went from minus5.55±2.59 to 2.43±0.94 (p<0.05) and BTI (PINP+DPD) fell from 17.26±5.25 to 4.47±2.31 (p<0.01). These data indicate increased bone turnover but decreased bone formation in both Paget's disease and hyperthyroidism. Following treatment bone turnover decreased to normal, and bone formation increased to a normal balance in both disorders. BTI and BRBI facilitate the interpretation of bone biomarkers and the monitoring of response to treatment.