Isolated skeletal involvement in Cushing's syndrome: response to therapy.

A 38-yr-old male presented with severe symptomatic osteopenia secondary to adrenal hyperfunction without any clinical expression of Cushing's syndrome. The predominantly axial distribution of his osteopenia and the presence of rib fractures healing with abundant callus formation, despite insignificant elevations in serum alkaline phosphatase, were characteristic of glucocorticoid excess syndromes. The histological features of the pretreatment bone biopsy were typical of those associated with excess glucocorticoids, namely decreased quantities of nonmineralized bone matrix, reflecting sites of bone formation, and an increase in the number of osteoclasts, indicating enhanced bone resorption. Six weeks after adrenalectomy, repeat bone biopsy revealed a marked increase in bone matrix synthesis and a significant decrease in bone resorption. These observations suggest that stimulators of skeletal turnover, like sodium fluoride, may be inappropriate in the initial treatment of steroid-induced osteopenia after surgical cure and that vitamin D and calcium therapy offers a more rational approach. Furthermore, the importance of the routine evaluation of adrenal function in any patient presenting with osteopenia is stressed, as well as the fact that relatively isolated skeletal involvement, classically described in micronodular adrenal disease, is not necessarily peculiar to a specific subset of the syndrome but may potentially attend any cause of glucocorticoid excess.