Bones tend to become less dense. Moderate loss of bone density is called osteopenia and severe loss of bone density (including occurrence of a fracture due to loss of bone density) is called osteoporosis. With osteoporosis, bones become weaker and more likely to break. In women, loss of bone density speeds up after menopause because less estrogen is produced. Estrogen helps prevent too much bone from being broken down during the body’s normal process of forming, breaking down, and re-forming bone.