TYPES OF OSTEOPOROSIS

Feature

Type I

Type II

Female:male ratio

6:1

2:1

Age range

51-65

> 75

Type of bone affected 

Trabecular

Cortical/trabecular

Typical fracture sites

Vertebrae, wrist

Hip

Type of bone loss

Accelerated

Gradual

Pathophysiology

Increased resorption

Decreased formation


Two different types of involutional osteoporosis have been described, although both types are actually end-state conditions as opposed to specific diseases.9 Type I osteoporosis, or "high turnover" osteoporosis, occurs most frequently in postmenopausal women between the ages of 51 and 65. Other features include a diminishing amount of trabecular bone and fractures of the vertebrae and wrist. The pathophysiologic defect in this type of osteoporosis is thought to be due to increased bone resorption due to estrogen deficiency.

Type II osteoporosis is also sometimes referred to as "senile" osteoporosis, and occurs more often in men than type I osteoporosis, but still predominantly affects women. This category is associated with more gradual bone loss that affects cortical and trabecular bone equally, and is thought to be due to decreased bone formation. Women are probably more commonly affected with Type II osteoporosis than men, because risk for fractures accumulates over a lifetime, and women have the residual effects of menopausal bone loss.

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