Ectopic adrenocorticotropin syndrome caused by lung cancer that responded to corticotropin-releasing hormone.

ACTH responses to corticotropin-releasing hormone (CRH) were studied in three patients with the ectopic ACTH syndrome caused by lung cancer. Plasma ACTH responded to synthetic CRH in two of three patients. Tumor tissues obtained from these two patients contained CRH and ACTH. In one patient, tumor ACTH secretion was stimulated by CRH in vitro. Tumor CRH was immunologically, chromatographically, and biologically similar to hypothalamic CRH. In addition, multiple forms of immunoreactive beta-endorphin were present in plasma and the tumor extracts. From these results, we conclude that some patients with the ectopic ACTH syndrome have tumors that produce both ACTH and CRH and that CRH can stimulate ACTH secretion by such tumors. Other patients with the ectopic ACTH syndrome do not have ACTH responses to CRH. Therefore, procedures other than CRH testing are needed to differentiate patients with Cushing's syndrome due to ectopic ACTH/CRH production from those with Cushing's disease, since the latter also usually have ACTH responses to CRH.