**6. Non-invasive markers of bone turnover in normal men and in men with prostate carcinoma treated with androgen deprivation therapy**

The slow dynamics of bone turnover and the infrequency with which bone density is monitored following castration in prostate cancer cases justify the recent increasing interest in studying the effects of ADT and the pathophysiology of bone metastasis.

Bone loss in elderly men occurs predominantly as a result of increased bone turnover. On bone histomorphometry, trabecular plate thinning and endocortical bone resorption is evident (Clarke BL, 1996). Non-invasive serologic and urinary markers of bone turnover now can be quantitated accurately. Markers of bone formation, such as bone-specific serum alkaline phosphatase, osteocalcin, procollagen type I propeptides and bone glaprotein, are usually normal in elderly men; whereas markers of bone resorption, such as urinary deoxypyridinoline excretion rates and the NTx and CTx telopeptides of Type I collagen and pyridinolines, often are found to be elevated (Khosla S, 1998).
