A Case of an Ectopic ACTH-Producing Tumor With Adrenal Shrinkage During Osilodrostat Administration

Ectopic adrenocorticotropin (ACTH)-secreting tumors are among the causes of ACTH-dependent Cushing syndrome. When surgical resection of the primary lesion is not feasible, medications such as metyrapone, mitotane, and ketoconazole have been used to control hypercortisolism. This report presents a case treated with the novel drug osilodrostat, wherein the patient's adrenal glands exhibited shrinkage following the initiation of this drug. The case involves a 68-year-old man diagnosed with small cell lung cancer and ectopic ACTH-producing Cushing syndrome. Initially, metyrapone was administered to manage hypercortisolism, but its effect proved insufficient. Subsequently, osilodrostat was initiated while gradually decreasing metyrapone, leading to full suppression of blood cortisol levels. With continued osilodrostat treatment, the adrenal glands reduced in size, suggesting the potential to reduce the osilodrostat dosage.