Incidence of Nelson's syndrome and residual adrenocortical function in patients of Cushing's disease after bilateral adrenalectomy.

Eighteen patients of Cushing's Disease, who had undergone bilateral "total" adrenalectomy 2 to 10 years back, were evaluated for residual adrenocortical function and for any evidence of Nelson's Syndrome. Surprisingly, all patients were discovered to have measurable plasma cortisol, albeit in the subnormal range. The standard criteria for accepting "completeness of adrenalectomy" were fulfilled in 16 patients. It was possible to wean one patient off replacement therapy. Thus, the dose of replacement steroids needs to be regulated according to the blood steroid levels in order to avoid unnecessary hypercortisolism. Radiological evidence of pituitary tumor diagnosed Nelson's Syndrome in 2 patients. Nelson's Syndrome was further suspected in 8 others who showed pigmentation. One of these had an enlarged sella and an erosion of the dorsum sellae, but had a normal CT scan. Another patient had evidence of incidental pituitary pathology (incidentaloma) which resolved spontaneously. Contrast enhanced CT scans of the sella are necessary for early detection of Nelson's Syndrome.