[Cushing's disease caused by adrenocortical nodular hyperplasia--diagnosis and surgical treatment]

Six cases of Cushing's disease, in which perplex diagnostic problem was encountered, were reported. In the endocrinological examination two cases were not suppressed by a high dose of dexamethasone (8 mg), and the other four cases showed complicated clinical findings due to adrenocortical nodular hyperplasia. Among those four cases with adrenocortical nodular hyperplasia two of them were of functionally autonomic and showed different attitude in responding endocrine assay. When the serum cortisol is not suppressed by a high dose of dexamethasone, differential diagnosis from other causes, such as Cushing's syndrome due to adrenocortical macronodular hyperplasia, becomes quite important for surgical treatment. Usually plasma ACTH in the case of Cushing's disease is slightly increased over the normal range and, on the other hand, it is lower than normal value in the case of Cushing's syndrome due to autonomic adrenocortical nodular hyperplasia because of negative feed back phenomenon. However, in some cases of Cushing's disease plasma ACTH is within normal range or even lower than normal level, and, furthermore, it is not extremely unusual to find a case of adrenocortical macronodular hyperplasia with slightly increased plasma ACTH level over normal range. Those cases offer particularly complex problem in making diagnosis and therapeutic indication. According to our clinical experiences with those six cases, selective venous sampling is found quite useful in differentiating Cushing's disease from other causes and ACTH value in selective venous sampling from inferior petrosal vein is remarkably increased in the cases due to pituitary ACTH secreting adenoma. Cushing's disease with adrenocortical nodular hyperplasia reduces the ACTH value in the sampling to the lower normal range as the adrenocortical nodular hyperplasia progresses.(ABSTRACT TRUNCATED AT 250 WORDS)