The most common cause is use of oral steroid drugs. The degree of bone loss often depends upon the steroid dose and duration of treatment. The rate of bone loss is highest in the first three to six months of steroid use, after which it slows.
Osteoporosis is one of the most common side effects of long-term treatment with oral steroids.
Not all types of steroids cause secondary osteoporosis. Oral corticosteroids such as prednisone have been clearly shown to weaken bone.