Clinical heterogeneity of involutional osteoporosis: Implications for preventive therapy

Involutional osteoporosis, the common form of osteo-porosis, begins in middle life and becomes progressively more frequent with advancing age. Although it has been suggested that the disorder is heterogeneous, until recently it was generally believed that it is a single entity. We have hypothesized (1, 2) that involutional osteoporosis can be divided into two distinct syndromes, type I (postmenopausal) osteoporosis and type II (age-related) osteoporosis. Here we review and update this hypothesis and point out its implications for preventive therapy. Type I osteoporosis typically affects women within 15–20 yr after their menopause. It is characterized by fractures that occur at sites rich in cancellous bone, “crush fractures” of the vertebrae, Colles’ fracture of the distal forearm, and fractures of the ankle. Type II osteoporosis can occur at any age but is the predominant form in both men and women age 70 and older; it is twice as common in women. It is characterized by fractures.