Ectopic ACTH-secreting syndrome: a single-center experience.

Objective: Ectopic adrenocorticotropic hormone (ACTH)-secreting syndrome (EAS) is a rare cause of ACTH-dependent endogenous hypercortisolism. The objective of this study was to analyze clinical, biochemical, and imaging characteristics; management strategies; and outcomes of EAS patients. Method: We screened the records (1993-2012) of ACTH-dependent endogenous hypercortisolism cases managed at a tertiary care center. Results: Of the 218 patients, 17 were diagnosed with EAS. The median 8:00 am serum cortisol was 36 mu g/dL (11.4-82.7 mu g/dL), and the median basal plasma ACTH was 156 pg/mL (53.5-468 pg/mL). Notably, ACTH levels below 100 pg/mL were found in 4 patients. Suspicious microadenoma was found on magnetic resonance imaging (MRI) of the pituitary in 5 patients, and all of them underwent transsphenoidal surgery (TSS). Inferior petrosal sinus sampling (IPSS) was performed in 8 patients, and the results were suggestive of a peripheral source in all 8. Computed tomography (CT) localized the lesion in 15/17 patients. In 2 patients with negative CTs, gallium DOTATATE positron emission tomography (PET) scans localized the lesion. Despite difficulties localizing bronchial carcinoids, the cure rate was high (72%). In contrast, thymic carcinoids were easily localized but had poor outcomes. Conclusion: EAS cannot be ruled out on the basis of marginally elevated ACTH. In cases with an equivocal MRI pituitary finding, prior IPSS can help avoid unnecessary TSS. CT is a useful modality for localization of an ectopic source. Functional imaging may help in cases where anatomical imaging fails.