Posterior subcapsular cataract in endogenous Cushing syndrome: an uncommon manifestation.

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Abstract

PURPOSE: Posterior subcapsular cataract is a well-known complication of longstanding glucocorticoid therapy (exogenous Cushing syndrome). The purpose of this study was to examine the effect of chronic endogenous hypercortisolism (endogenous Cushing syndrome) on the human lens. METHODS: Sixty consecutive patients (8 to 67 years of age, 46 females, 14 males) with endogenous Cushing syndrome were studied. The exposure to cortisol was estimated based on the duration of the disease and measurements of the 24-hour urine free cortisol excretion. Complete ocular examination included biomicroscopy of the lens after dilation. RESULTS: Duration from the onset of endogenous Cushing syndrome ranged from 1 to 20 years (mean +/- SD, 5.5 +/- 3.7). Urine free cortisol excretion ranged from 250 to 3065 micrograms/24 hr (mean +/- SD, 693 +/- 547; normal values, 20 to 90 micrograms/24 hr). Only two of the 60 patients (3.3%) had posterior subcapsular cataract. This low prevalence contrasts to the high prevalence attributed to glucocorticoid therapy with grossly equivalent total dosage of glucocorticoids. CONCLUSION: It was concluded that posterior subcapsular cataract is an infrequent complication of endogenous hypercortisolism compared to exogenous Cushing syndrome. Because the total exposure to endogenous glucocorticoids was not lower than that of exogenous glucocorticoid therapy, a potential explanation for this difference might be the exposure of the lens to the natural (cortisol) rather than a synthetic glucocorticoid or pharmacokinetic differences of glucocorticoids between the two forms of Cushing syndrome.