Occult Carcinoid Causes Cushing’s Syndrome
Authors: Meftali Sabrina , Unterborn Rebecca , Gifford Amanda , Bhatt Bankim 
Published: May 2021

Abstract
Introduction: Lung neuroendocrine tumors (NETs) are a common cause of ectopic ACTH-secretion. Only 3% of NETs cause Cushing’s syndrome1; the majority are small and may be radiographically occult. Additionally, the responses to dexamethasone, metyrapone, and oCRF can be indistinguishable from that observed in pituitary Cushing’s disease2. These challenges lead to misdiagnosis and unnecessary procedures. Case Description: 45-year-old male presented for resection of right-sided pulmonary carcinoid tumor. He was diagnosed with Cushing’s syndrome in 2011 when he experienced uncontrolled hypertension and excessive weight gain with elevations in cortisol and ACTH levels. He underwent transsphenoidal pituitary resection in May 2011 for a possible pituitary microadenoma. Post-operative worsening hypertension, weight gain, and striae led to bilateral adrenalectomy in November 2011, complicated by retroperitoneal hemorrhage and resuscitation-induced pulmonary edema. On chest CT in early 2012, an 8 mm incidental right pulmonary nodule was documented. 8 years later, chest imaging for mild COVID-19 infection again revealed a right-sided pulmonary nodule. He underwent CT-guided biopsy of the nodule in July 2020 with pathology demonstrating carcinoid histology. Right lower lobectomy was performed. Pre-operative ACTH was 1673 pg/mL (normal: 10-60 pg/mL) and post-operative ACTH was 16 pg/mL. The resected tumor stained positive for ACTH, confirming that carcinoid tumor was the source of Cushing’s for the past decade.
Conclusion: The diagnosis of ectopic Cushing’s syndrome can be elusive, leading to surgeries with significant morbidity, as seen in our patient. In one retrospective review, 14% of patients with Cushing’s had transsphenoidal resection before they were diagnosed with an ectopic source3. Ectopic Cushing’s syndrome can be a challenging diagnosis to make and a multidisciplinary approach with close collaboration between endocrinologist, radiologist, surgeon and pathologist may increase the diagnosis accuracy.
Citations: 1Kamp, K, Alwani, R A, Korpershoek, E, Franssen, G., de Herder, W W, & Feelders, R A. (2016). Prevalence and clinical features of the ectopic ACTH syndrome in patients with gastroenteropancreatic and thoracic neuroendocrine tumors, European Journal of Endocrinology, 174(3), 271-280. Retrieved Jan 15, 2021, from https://eje.bioscientifica.com/view/journals/eje/174/3/271.xml
2Malchoff CD, Orth DN, Abboud C, Carney JA, Pairolero PC, Carey RM. Ectopic ACTH syndrome caused by a bronchial carcinoid tumor responsive to dexamethasone, metyrapone, and corticotropin-releasing factor. The American Journal of Medicine. 1988;84(4):760-764. doi:10.1016/0002-9343(88)90116-7
3Ioannis Ilias, David J. Torpy, Karel Pacak, Nancy Mullen, Robert A. Wesley, Lynnette K. Nieman,Cushing’s Syndrome Due to Ectopic Corticotropin Secretion: Twenty Years’ Experience at theNational Institutes of Health, The Journal of Clinical Endocrinology & Metabolism, Volume 90, Issue8, 1 August 2005, Pages 4955–4962, https://doi.org/10.1210/jc.2004-2527