The statistics surrounding osteoporosis are astounding. More than 1.3 million fractures occur each year as a result of this condition. Eighty percent of the 250,000 hip fractures in the United States each year occur in women over age 65 as a result of osteoporosis. About one-quarter of these women die within one year from complications, such as blood clots and pneumonia, caused by their convalescence. Another one-third never regain the ability to function physically or socially on their own. These women spend the rest of their lives requiring long-term care in nursing facilities. In addition to causing hip fractures, osteoporosis is also responsible for loss of bone in the jaw, gum recession (both of which are early signs of this condition), dowager's hump, loss of height, back pain due to compression and fractures of the vertebra, and fractures of the wrist (called colles fractures by physicians).

Often these fractures occur when only mild stress is put on the bone. This can include missing a step and falling down, falling on an extended arm or lifting a heavy object. Because of the underlying weakness of the bone, fractures can also occur spontaneously without any preceding trauma. This often occurs with vertebral fractures.

This chapter will discuss what happens to bones with osteoporosis, risk factors for osteoporosis, diagnosis of osteoporosis and other structural changes associated with menopause. Finally, therapies for osteoporosis and other structural changes will be explored.

What Happens to Bones with Osteoporosis
Bones are living tissue; we are constantly forming new bone cells to add to our skeletal mass and removing old cells that are no longer useful. This simultaneous addition and subtraction of bone from our skeleton is called bone remodeling; from five to ten percent of our bone is replaced through this process every year. Bone remodeling involves two types of bone cells. Osteoblasts create new bone cells, while osteoclasts are responsible for removing old cells from the skeleton. This delicately balanced process is carefully regulated by many of the hormones in our body such as estrogen, progesterone, calcitonin and thyroid (as well as other hormones).

During the first 30 to 35 years of life, we deposit more bone in our skeleton than we lose, provided our health status is normal. In fact, our bone mass is at its peak in our 20s and begins to decrease in the mid-30s. According to peak bone mass theory, our bones reach their peak level of healthy density by the early 20s. The more healthy our bones are at this stage, the less risk of osteoporosis later in life. In the years preceding menopause, bone loss begins to exceed the addition of new bone to the skeleton. As a result, bones begin to lose important minerals such as calcium, as well as their matrix or intracellular substance. This causes a decrease in bone density as well as an increased brittleness or porousness of the bones

Initially, this process occurs very slowly, and women are not even aware that it is going on. However, with loss of hormonal support to the bones at the time of menopause, this process accelerates. The first years after the onset of menopause can be a time of rapid bone loss for many women unless they have instituted therapies that emphasize prevention. Bone is lost at the rate of one to three percent per year for five to ten years after menopause. If the process of bone loss continues unabated, osteoporosis may eventually result. Unfortunately, most women are unaware that they are losing bone during their early postmenopausal years. By the time osteoporosis becomes apparent as they begin to suffer from pain and fractures, women are already in their 60s or 70s. Older women with osteoporosis may have lost as much as 40 to 45 percent of their total bone mass.