Ectopic adrenocorticotrophic hormone syndrome secondary to treatment-related neuroendocrine differentiation of metastatic castrate-resistant prostate cancer

Abstract

A 64-year-old man with progressive metastatic castrate-resistant prostate adenocarcinoma presented with recurrent fluid overload, severe hypokalaemia with metabolic alkalosis and loss of glycaemic control. Clinical features were facial plethora, skin bruising and proximal myopathy. Plasma adrenocorticotrophic hormone (ACTH), serum cortisol and 24-h urinary cortisol levels were elevated. Low-dose dexamethasone failed to suppress cortisol. Pituitary MRI was normal and 68Gallium-DOTATATE PET–CT scan showed only features of metastatic prostate cancer. He was diagnosed with ectopic ACTH syndrome secondary to treatment-related neuroendocrine prostate cancer differentiation. Medical management was limited by clinical deterioration, accessibility of medications and cancer progression. Ketoconazole and cabergoline were utilised, but cortisol remained uncontrolled. He succumbed 5 months following diagnosis. Treatment-related neuroendocrine differentiation of prostate adenocarcinoma is a rare cause of ectopic ACTH syndrome.