An Evaluation of the Distinction of Ectopic and Pituitary ACTH Dependent Cushing's Syndrome by Clinical Features, Biochemical Tests and Radiological Findings

摘要

The efficiency of various laboratory and radiological investigations in the differentiation of ectopic from pituitary dependent Cushing's syndrome was studied, based on findings in 23 patients with verified Cushing's disease and seven patients with the ectopic ACTH syndrome.Clinical features strongly favouring the ectopic type were male sex and history for less than 18 months. Basal biochemical features strongly indicating the ectopic syndrome included plasma K+30 mmol/l; serum cortisol at 9 a.m. or midnight of>800 nmol/l; urine free cortisol>1300 nmol/24 hours; plasma ACTH>100 ng/1.In the high-dose dexamethasone suppression test, suppression by450nmol/l for the 9 a.m. and midnight cortisol combined occurred in all of those with the ectopic syndrome, but in none of the 23 patients with Cushing's disease. For urine free cortisol, a mean suppressed value of3-fold in all but one of the patients with Cushing's disease.Failure to respond to either dexamethasone or metyrapone was found in only one of the patients with Cushing's disease (Patient 16); in the ectopic group, all patients exceptPatient Dfailed to respond to either test.It is concluded that patients presenting with clinically obvious Cushing's syndrome along with measuranle plasma ACTH can be reliably divided by conventional tests into those that are driven from the pituitary and those driven by ectopic ACT