i was diagnosed with premature borderline osteoporosis about 2 years ago, have had 2 bone density scans and it hadnt changed in the 12 months between the scans. initially, i was told that the condition of my bones was due to having crohns disease for so many years, and particularly during my teens when bones should be getting stronger through dietary calcium absorbtion. however, it was later found that my two siblings also had early osteoporosis, and therefore mine is probably a mixture of genetic and crohns factors.
however, it does mean that the medical profession recognise crohns as a cause of calcium depletion, quite possibly the same would apply to any long-standing debilitating illness.
i never had steroid treatment back then, so that can be discounted, in my case.
dingbat.