Osteoporosis is a metabolic disease of bone characterized by porous, weak, and brittle bones. It is common in post-menopausal women and the elderly due to changes in hormone levels. Some risk factors include being thin, deficient in calcium or vitamin D, lack of exercise, and certain medical conditions or medications. Symptoms include back pain and increased risk of fractures in the wrists, hips, or vertebrae. Diagnosis involves a DEXA scan or x-rays to measure bone mineral density.