POSTERIOR SUBCAPSULAR CATARACT IN ENDOGENOUS CUSHING SYNDROME - AN UNCOMMON MANIFESTATION

Purpose. Posterior subcapsular cataract is a well-known complication o f longstanding glucocorticoid therapy (exogenous Cushing syndrome). Th e purpose of this study was to examine the effect of chronic endogenou s hypercortisolism (endogenous Cushing syndrome) on the human lens. Me thods. Sixty consecutive patients (8 to 67 years of age, 46 females, 1 4 males) with endogenous Cushing syndrome were studied. The exposure t o cortisol was estimated based on the duration of the disease and meas urements of the 24-hour urine free cortisol excretion. Complete ocular examination included biomicroscopy of the lens after dilation. Result s. Duration from the onset of endogenous Cushing syndrome ranged from 1 to 20 years (mean +/- SD, 5.5 +/- 3.7). Urine free cortisol excretio n ranged from 250 to 3065 mug/24 hr (mean +/- SD, 693 +/- 547; normal values, 20 to 90 mug/24 hr). Only two of the 60 patients (3.3%) had po sterior subcapsular cataract. This low prevalence contrasts to the hig h prevalence attributed to glucocorticoid therapy with grossly equival ent total dosage of glucocorticoids. Conclusion. It was concluded that posterior subcapsular cataract is an infrequent complication of endog enous hypercortisolism compared to exogenous Cushing syndrome. Because the total exposure to endogenous glucocorticoids was not lower than t hat of exogenous glucocorticoid therapy, a potential explanation for t his difference might be the exposure of the lens to the natural (corti sol) rather than a synthetic glucocorticoid or pharmacokinetic differe nces of glucocorticoids between the two forms of Cushing syndrome.