In a normal, healthy adult, bone is continually absorbed into the body and then rebuilt. During childhood and the teen years, new bone tissue is added faster than existing bone is absorbed. As a result, your bones become larger and heavier until about age 30 when you reach peak bone mass (density). The more bone mass you developed early in life, the less likely you are to develop osteoporosis.
After age 30, both men and women lose a small amount of bone each year. Because most men build greater bone mass than women do, they tend to get osteoporosis later in life.
A person with thinning bones may be diagnosed with lower-than-normal bone mass (osteopenia). Osteopenia sometimes progresses to osteoporosis.
When bones thin, they lose strength and break more easily. The bones that break most often due to osteoporosis are:
- The spine. About half of broken bones caused by osteoporosis are bones in the spine. Men and women who have a spinal fracture have a higher risk of future spinal fractures. Vertebrae that are weak because of osteoporosis may break and collapse on top of each other (compression fracture). Compression fractures of the spine can result in back pain, stooped posture, loss of height, and a curved upper back (dowager's hump).
- The hip. Hip fractures are most common in older women. Hip fractures are often caused by a fall. They can make it very hard for you to move around and they usually require major surgery. After a hip fracture, many older people have medical complications such as blood clots, pressure sores, or pneumonia.
- The wrist and forearm.
In women, bone loss increases when the ovaries reduce production of estrogen, a hormone that protects against bone loss. Studies show that on average, women lose 1% to 3% of their bone mass every year for about 3 to 5 years after menopause.
In men, the hormone testosterone protects against bone loss. Osteoporosis develops most often in men older than 65.
See a picture of healthy bone versus bone weakened by osteoporosis.