Differential diagnosis and secondary causes of osteoporosis.

Secondary osteoporosis refers to osteoporosis in which an underlying cause or factor other than those attributable to the postmenopausal state or aging can be identified. Primary, or idiopathic, osteoporosis implies that a secondary cause cannot be found. Secondary osteoporosis occurs not only in postmenopausal women but also in men and premenopausal women. In series reported from specialized centers, as many as 30% of postmenopausal women and 50% to 80% of men have an identifiable secondary cause of osteoporosis, although the frequency of secondary osteoporosis is probably much lower in the general population. In assessing the patient with osteoporosis, it is important to look for secondary causes and aggravating factors that are reversible and amenable to therapy. In addition to secondary forms, 2 metabolic bone diseases, osteomalacia and primary hyperparathyroidism, can mimic or aggravate osteoporosis. This paper will summarize the differential diagnosis and management of osteoporosis, osteomalacia, and hyperparathyroidism and review the most common causes of secondary osteoporosis.