Bones are made of complex, constantly changing, living tissue. They are able to grow and heal, and are also susceptible to changes in diet, body chemistry, and exercise levels. These are the changes that can lead to osteoporosis.
Early in life, more bone is laid down than is removed by the body. People typically achieve peak bone mass by around age 30, after which more bone is lost than is replaced. Too much bone loss leads to osteoporosis.
Both of the two primary types of osteoporosis are far more common in women than men:
- Type I osteoporosis (postmenopausal osteoporosis) generally develops after menopause, when estrogen levels drop precipitously. These changes lead to bone loss, usually in the trabecular (spongy) bone inside the hard cortical bone.
- Type II osteoporosis (senile osteoporosis) typically happens after age 70 and involves a thinning of both the trabecular (spongy) and cortical (hard) bone.
In addition, certain medications and medical conditions can damage bone and lead to what is known as "secondary osteoporosis." Patients being treated for any of the following conditions should discuss the risk of osteoporosis with their physicians:
- Endocrine disorders
- Marrow disorders
- Collagen disorders
- Gastrointestinal disorders
- Seizure disorders
- Eating disorders (such as anorexia or bulimia)
It is important to distinguish between primary and secondary causes of osteoporosis because treatment is often different. To determine the cause, a thorough medical history, physical examination, and appropriate diagnostic tests need to be conducted (see Diagnosing Osteoporosis).
Key risk factors for developing osteoporosis include:
- Advanced age. Osteoporosis occurs frequently in those over age 65.
- Gender. Women are four times more likely to develop osteoporosis than men.
- Heredity. Family history of osteoporosis or fracture on the mother’s side.
- Personal history. Any type of fracture after age 45.
- Race. Caucasian and Asian women are at greater risk.
- Body type. Small-boned women weighing less than 127 pounds.
- Menstrual history. Normal menopause increases the risk of osteoporosis and early menopause can exacerbate this risk.
- Lifestyle. Risk factors include calcium and/or vitamin D deficiency; little or no exercise (especially weight-bearing exercise); alcohol abuse; smoking; too much cola/soda.
- Testosterone deficiency (hypgonadism) in men.