Objectives To better understand bone metabolism and predict bone loss in treatment using gonadotropin-releasing hormone agonist for patients with prostate cancer. Methods The changes in bone mineral density and blood levels of bone metabolism markers and the level of pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen, a specific marker of bone resorption, and carboxy-terminal pro-peptide of human type I procollagen, a specific marker of bone formation, were examined in 27 consecutive patients with prostate cancer without bone metastasis. Results After 2 years of gonadotropin-releasing hormone treatment, the bone mineral density was significantly lower (median 0.937 g/cm2) than before treatment. Pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen began to increase significantly 6 months after the start of treatment (3.0 to 8.3 ng/mL, median 4.6, at baseline versus 3.4 to 8.2 ng/mL, median 5.2, after 6 months). Carboxy-terminal pro-peptide of human type I procollagen began to show a significant rise 1 year after the start of treatment (from 72.8 to 221.5 ng/mL, median 102.0, at baseline to 82.7 to 293.4 ng/mL, median 132.0, at 1 year). Conclusions Functional coupling between bone resorption and formation was noted, and a decrease in bone mass, even in men, owing to androgen deficiency, was biochemically demonstrated. Fluctuations in these two bone metabolism markers preceded the decrease of bone mineral density. Therefore, these markers might be a predictor of bone loss.
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