Parallel assays of β-endorphin and ACTH in cushing's patients undergoing petrosal sinus sampling

This study explores the possibility of improving endocrinologic testing during petrosal sinus catheterization by determining both β-endorphin and corticotropin (ACTH). We studied 14 patients with Cushing's disease, two with adrenal tumor, and three with ectopic tumors secreting ACTH. In patients with Cushing's disease, β-endorphin concentrations paralleled those of ACTH in all basal plasma samples collected either from petrosal sinuses or peripheral veins. Individual responses of β-endorphin and ACTH to corticotropin releasing hormone (CRH) were closely related to the presence of a corticotroph adenoma. In such patients, a consistently higher concentration of β-endorphin over ACTH was observed in all samples collected either from petrosal sinuses or peripheral veins; the ratios were unchanged after the administration of CRH. In patients with ectopic ACTH secretion, the mean ratio of β-endorphin over ACTH (with both values expressed in pmol/L) was significantly higher (3.5) than that of patients with Cushing's disease (2.9) or Cushing's syndrome due to adrenal tumor (2.7).