From the National Institutes of Health's Osteoporosis and Related Bone Diseases ~ National Resource Center
Osteoporosis, or porous bone, is a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased risk of fractures of the hip, spine, and wrist. Men as well as women are affected by osteoporosis, a disease that can be prevented and treated. In the United States, more than 40 million people either already have osteoporosis or are at high risk due to low bone mass.
What Is Bone?
Bone is living, growing tissue. It is made mostly of collagen, a protein that provides a soft framework, and calcium phosphate, a mineral that adds strength and hardens the framework.
This combination of collagen and calcium makes bone both flexible and strong, which in turn helps it to withstand stress. More than 99 percent of the body's calcium is contained in the bones and teeth. The remaining 1 percent is found in the blood.
Throughout your lifetime, old bone is removed (resorption) and new bone is added to the skeleton (formation). During childhood and teenage years, new bone is added faster than old bone is removed. As a result, bones become larger, heavier, and denser. Bone formation outpaces resorption until peak bone mass (maximum bone density and strength) is reached around age 30. After that time, bone resorption slowly begins to exceed bone formation.
For women, bone loss is fastest in the first few years after menopause, and it continues into the postmenopausal years. Osteoporosis — which mainly affects women but may also affect men — will develop when bone resorption occurs too quickly or when replacement occurs too slowly. Osteoporosis is more likely to develop if you did not reach optimal peak bone mass during your bone-building years.
Osteoporosis is often called the "silent disease" because bone loss occurs without symptoms. People may not know that they have osteoporosis until their bones become so weak that a sudden strain, bump, or fall causes a hip to fracture or a vertebra to collapse. Collapsed vertebrae may initially be felt or seen in the form of severe back pain, loss of height, or spinal deformities such as kyphosis (severely stooped posture).
Following a comprehensive medical assessment, your doctor may recommend that you have your bone mass measured. A bone mineral density (BMD) test is the best way to determine your bone health. BMD tests can identify osteoporosis, determine your risk for fractures (broken bones), and measure your response to osteoporosis treatment. The most widely recognized bone mineral density test is called a dual-energy x-ray absorptiometry or DXA test. It is painless — a bit like having an Xray, but with much less exposure to radiation. It can measure bone density at your hip and spine. Bone density tests can:
- Detect low bone density before a fracture occurs.
Confirm a diagnosis of osteoporosis if you already have one or more fractures.
Predict your chances of fracturing in the future.
Determine your rate of bone loss, and/or monitor the effects of treatment if the test is conducted at intervals of a year or more.