As defined by the World Health Organization, osteoporosis is a generalized skeletal disorder of low bone mass (thinning of the bone) and deterioration in its architecture, causing susceptibility to fracture.

There are two types of osteoporosis:

  1. Type I osteoporosis (postmenopausal osteoporosis) generally develops in women after menopause when the amount of estrogen in the body greatly decreases. This process leads to an increase in the resorption of bone (the bones loses substance).

    Type 1 osteoporosis is far more common in women than in men, and typically develops between the ages of 50 and 70. The process usually results in a decrease in the amount of trabecular bone (the spongy bone inside of the hard cortical bone). The decrease in the overall strength of the bone leads primarily to wrist and vertebral body (in the spine) fractures.
  2. Type II osteoporosis (senile osteoporosis) typically happens after the age of 70 and affects women twice as frequently as men.

    Type II osteoporosis involves a thinning of both the trabecular bone (the spongy bone inside of the hard cortical bone) and the hard cortical bone. This process often leads to hip and vertebral body fractures.

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There is some overlap between the two types of osteoporosis. The type that can be significantly influenced and prevented is Type I osteoporosis (postmenopausal osteoporosis) from estrogen deficiency.

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It is important to note that osteoporosis may either be a primary problem (Type I or Type II) or may be secondary to another problem. Approximately 20% of women and 40% of men with osteoporosis have a secondary cause of osteoporosis, such as hyperthyroidism or lymphoma. See Osteoporosis Diagnosis for additional secondary causes. In order to determine the cause of osteoporosis, a thorough medical history and physical examination, as well as the appropriate diagnostic tests, need to be obtained.