Cushing Syndrome (CS) secondary to an ectopic ACTH-secreting tumor has been scarcely reported in the literature

We describe a case of severe CS secondary to an ACTH-secreting medullary thyroid carcinoma (MTC)

A 62-year-old male with a past medical history of hypertension, ischemic cardiopathy, and recent pulmonary embolism complicated with a spontaneous retroperitoneal hematoma was admitted in February 2022 for pneumonia and heart failure. The patient developed severe hypokalemia which was managed by Endocrinologists and was finally diagnosed with CS with ectopic production of ATCH. Serum calcitonin levels requested as part of the workout were high (290 pg/mL). US showed an 8 mm TIRADS-5 right nodule with inconclusive cytology and 68Ga-DOTATOC PET-CT showed increased uptake in the right thyroid lobe and right laterocervical lymph nodes, suggesting a MTC. In March 2022, a total thyroidectomy with bilateral central and right lateral neck dissection was performed. The pathology report informed of a right 14 mm CMT with 4/7 and 3/9 positive lymph nodes in central and lateral compartments, respectively. The patient developed postoperative hypoparathyroidism and was discharged on 37 postoperative day because of severe myopathy and malnutrition. Genetic testing was negative and at 18 months of follow-up calcitonin is stable (22.1pg/mL), ACTH and cortisol levels remain normal and US shows no signs of recurrence.

CMT should be considered among the causes of ectopic CS and is generally associated with advanced disease and prolonged admission