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

OBJECTIVES Increased urinary albumin excretion (UAE) in diabetic and nondiabetic subjects is frequently associated with insulin resistance syndrome and central obesity. Cushing's syndrome is also characterized by central obesity and insulin resistance. This study was undertaken to see whether increased UAE is found in Cushing's syndrome. DESIGN Cross-sectional study. PATIENTS Thirteen consecutive patients with Cushing's syndrome. MEASUREMENTS Patients collected three overnight urine samples for the measurement of UAE by radioimmunoassay. UAE was also measured in 479 nondiabetic subjects who comprised the control population for this study. In the patients who had initial microalbuminuria, UAE was remeasured 2 months after successful removal 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 μg/min), and eight patients (61.5%) had microalbuminuria or overt proteinuria (> 20 μg/min). Kidney biopsy revealed apparently normal glomerular structures without evidence of diabetic nephropathy. After correction of hypercortisolaemia, 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 hypercortisolaemia. These results indicate that endogenous hypercortisolaemia increases UAE by a mechanism that is presently unknown.