Rapid Recovery of Hypothalamic-Pituitary Axis after Successful Resection of an ACTH-secreting Neuroendocrine Tumor.

We describe a 30-year-old man with ectopic adrenocorticotropic hormone (ACTH) syndrome. Before the operation, there was no diurnal variation of ACTH, and ACTH did not respond to CRH or dexamethasone suppression tests. These abnormalities disappeared after the removal of a neuroendocrine tumor in the lung. In addition, plasma ACTH was measureable at as early as postoperative day 3 with ACTH levels increasing thereafter. Furthermore, an insulin tolerance test and inferior petrosal sinus sampling indicated that ACTH was secreted from the pituitary. This case indicates that the hypothalamic-pituitary function can recover within a couple of weeks after curative surgery for ectopic ACTH syndrome.