Supplemental Material for: Marked hypokalemia at presentation in an adolescent with ectopic ACTH syndrome secondary to a bronchial carcinoid tumor: a case report

Compared with Cushing's disease, EAS follows a more rapid clinical course with more pronounced metabolic disturbances, among which hypokalemia is one of the most distinctive features.</p><p dir="ltr">Case Presentation: A 14.7-year-old male presented with a three-month history of rapid weight gain, violaceous striae, hypertension, and proximal muscle weakness.

Markedhypokalemia (2.8 mmol/L) prompted endocrine work-up, which revealed ACTH-dependent hypercortisolism with loss of diurnal cortisol rhythm, elevated midnight salivary cortisol, and non-suppression on low- and high-dose dexamethasone suppression tests. Pituitary MRI was unremarkable, and the marked hypokalemia raised suspicion of an ectopic source. Thoracic CT identified a nodular lesion in the right middle lobe, with corresponding uptake on ⁶⁸Ga-DOTATATE PET/CT.