Increased urinary albumin excretion in Cushing's syndrome: remission aftercorrection of hypercortisolaemia

OBJECTIVES Increased urinary albumin excretion (UAE) in diabetic and nondia betic subjects is frequently associated with insulin resistance syndrome an d central obesity. Cushing's syndrome is also characterized by central obes ity and insulin resistance. This study was undertaken to see whether increa sed UAE is found in Cushing's syndrome. DESIGN Cross-sectional study. PATIENTS Thirteen consecutive patients with Cushing's syndrome. MEASUREMENT S Patients collected three overnight urine samples for the measurement of U AE by radioimmunoassay. UAE was also measured in 479 nondiabetic subjects w ho comprised the control population for this study. In the patients who had initial microalbuminuria, UAE was remeasured 2 months after successful rem oval of pituitary or adrenal tumours. Kidney biopsy was performed in three patients during adrenalectomy. RESULTS Eleven out of 13 patients (84.6%) had increased UAE (> 9.6 mu g/min ), and eight patients (61.5%) had microalbuminuria or overt proteinuria (> 20 mu g/min). Kidney biopsy revealed apparently normal glomerular structure s without evidence of diabetic nephropathy. After correction of hypercortis olaemia, UAE declined profoundly in all of the patients. CONCLUSIONS More than 80% of patients with Cushing's syndrome had increased UAE. This was almost completely reversed after successful treatment of hyp ercortisolaemia. These results indicate that endogenous hypercortisolaemia increases UAE by a mechanism that is presently unknown.