My understanding of the bone density test is that excess steroid intake can cause the bones to be weaker and potentially lead to arthritis.  My Endo had my get a bone density scan when I was 16 and then never said anything about getting another one.  

However, my work gives bone density scans to at risk people every 2 or 3 years and they send the results to my doctor.  And since I have become aware of the potential effects of excess steroid intake, I have started taking daily calcium tablets and drinking more milk.  And my bones were more dense at my latest scan.