Types of Osteoporosis

Osteoporosis is classified as primary if no other mechanism or disorder can be identified as responsible for the identified bone loss. It is classified as secondary if the bone loss occurs due to a prior existing condition or event, such as the use of certain medications or the simultaneous presence of another disorder.

Primary osteoporosis is further characterized into postmenopausal (Types I and II). Type I osteoporosis, or early postmenopausal osteoporosis, is characterized by an excessive loss of trabecular bone (the center area of the bone); while Type II patients lose both trabecular and cortical bone (outer layers of bone), and is an age-related disease. Decreases in estrogen levels is the critical event in women with osteoporosis, and the longer the postmenopausal period the greater the incidence of osteoporosis.

Among men with osteoporosis, approximately 50% have secondary osteoporosis, brought on by an underlying disease or medication. Because of this high percentage of secondary osteoporosis in men, all potential causes should be ruled out as part of the evaluation. Chronic corticosteroid use is the most common drug-related cause of secondary osteoporosis and is a particular issue for patients with rheumatoid arthritis, inflammatory bowel disease, systemic lupus erythematosus, asthma, and chronic lung diseases such as severe chronic obstructive pulmonary disease (COPD).