Why would I have low bone density if I haven't gone through menopause?

Although the drop in estrogen levels during menopause can result in dramatically worsening osteoporosis, it isn't the sole cause of the disease. Many other factors -- like your genes, some diseases and treatments, eating disorders, and deficiencies of calcium and vitamin D -- can play an important role. Remember that men can get osteoporosis too, even though they don't go through menopause.