Spontaneous adrenocorticotropic hormone (ACTH) normalisation due to tumour regression induced by metyrapone in a patient with ectopic ACTH syndrome: case report and literature review.

MTP and/or KTZ may reduce ACTH and cortisol production. The tumour spontaneously regressed after MTP treatment, indicating that MTP may reduce the tumour size without surgery. The mechanisms of therapeutic effects of steroidogenesis inhibitors and prognosis of spontaneous remission should be elucidated further via molecular biology studies.