Another 18 million Americans have low bone mass. In normal adults, bone mass peaks during adolescence and both men and women lose bone mass steadily throughout adult life. When bones start to thin too much, people develop a condition called osteopenia. If bone thinning becomes even more severe, the condition is called osteoporosis. Children at greatest risk of osteoporosis are those with rheumatoid arthritis or other conditions that require large doses of glucocorticoids, a class of steroids that decreases the rate at which bone mass accumulates, said Dr. Edward Giannini, professor of pediatrics at Children's Hospital Medical Center in Cincinnati.
Prednisone is one type of glucocorticoid.
For these children, severe bone loss can result in osteoporosis by the time they are teenagers. Another high risk group for osteoporosis are young women with eating disorders, such as anorexia nervosa, Klibanski said. These women can lose 25 percent to 50 percent of their bone mass within six months to a year when the eating disorder symptoms become severe, she said. Young women with low levels of estrogen pose another high risk category for osteoporosis. These are women who stop having menstrual cycles, and researchers are now trying to determine if teenage girls with infrequent menstrual cycles also are at risk of bone loss.