Evidence for ectopic ACTH production years after bilateral adrenalectomy for Cushing's syndrome: in vivo and in vitro studies.

Three patients presented with hyperpigmentation and high plasma levels of ACTH 4-5 years after bilateral adrenalectomy for Cushing's "disease". X-rays and ct-scan of the lungs showed a small pulmonary mass in all. ACTH levels (1100-2000 pg/ml) were not suppressible by high doses hydrocortisone. A carcinoid tumor was removed in two cases and a chemodectoma in the third. Evidence for ACTH secretion by these tumors was provided by both decrease of ACTH levels after surgery and/or in vitro studies. Both carcinoid cultures showed a basal ACTH production, which was clearly increased by LVP (10(-7) M) and CRF (10(-7) M). Our findings in vitro studies suggest the presence of specific receptor sites for physiological stimuli (LVP and CRF) in tumor cell membranes.