Lymph Node ACTH Washout: New Assistant Method for Localizing the Source of Ectopic ACTH Secretion in a Case of Metastatic Medullary Thyroid Carcinoma

Abstract In ACTH-dependent Cushing syndrome, identifying the source of ACTH can be challenging. A 23-year-old male presented with Cushingoid symptoms and signs to other clinics. Laboratory tests confirmed ACTH-dependent Cushing’s syndrome. Imaging revealed a suspicious adenoma in the pituitary, a hypoechoic nodule in the thyroid, and pathological-appearing lymph nodes in the neck. Following a fine needle aspiration cytological examination, medullary thyroid carcinoma was diagnosed. A total thyroidectomy and lymph node dissection were subsequently performed. The pathology report confirmed medullary thyroid carcinoma. When the patient was admitted to our hospital, disease recurrence was considered, and lymph node ACTH washout was performed as an unusual method to identify the source of ACTH. The washout sample yielded a very high value of 958 pg/mL. We describe a patient who was hospitalized with severe symptoms of Cushing’s syndrome resulting from medullary thyroid cancer. We employed a novel method involving lymph node ACTH washout to identify the source of ACTH production. Lymph node ACTH washout can be an effective diagnostic option to determine the origin of ACTH. Cite this article as: İşler AO, Şendur SN, Gönül İremli B, et al. Lymph node ACTH washout: new assistant method for localizing the source of ectopic ACTH secretion in a case of metastatic medullary thyroid carcinoma. Endocrinol Res Pract. 2024;28(4):229-232.