Prostate cancer treatments, particularly hormone therapy (ADT) can have a significant effect on speeding up the process of thinning and weakening the bones. There are some available treatments (Zoledronic acid aka Zoladex and denosumab aka Xgeva) which are designed to slow down or reverse this process; however, they are known to have many adverse side effects themselves.  These side effects can include severe fractures of the femur which could limit survival and cataracts.  For this reason, these treatments are usually used later, when men become castrate resistant and metastatic.