Glucocorticoids are the primary therapy for many inflammatory and autoimmune diseases, such as asthma, rheumatoid arthritis, and inflammatory bowel disease. They are also used to treat many allergic conditions. While these agents are generally effective in treating such ailments, they are also the most common cause of drug-induced osteoporosis.
Glucocorticoids affect calcium and bone metabolism in many ways.
Steroids decrease the amount of calcium absorbed by the intestine and increase calcium excretion through the kidneys. These two factors combine to produce a decline in the circulating ionized calcium concentration. Glucocorticoids can also decrease the levels of sex hormones, important regulators of bone metabolism in both men and women. Glucocorticoids also cause muscle weakness, which may lead to inactivity and additional bone loss. Cortical bone forms the outer shell of bone and comprises 80 percent of the skeleton.