Cushing’s syndrome due to ectopic production of adrenocorticotrophic-hormone (ACTH) is associated with a large range of tumours including small cell lung cancer and bronchial carcinoid most commonly. Prostate cancer causing Cushing syndrome is rare. We present the case of a 75yo man on chemotherapy for metastatic prostate small cell carcinoma who developed ACTH-dependent Cushing’s syndrome.
He presented with profound hypokalaemia, hypertension and new onset hyperglycaemia. Associated non-specific cushingoid features included generalised weakness and debility, lower limb oedema, central adiposity and low mood. Investigations confirmed Cushing’s syndrome with elevated 24 hour urinary free cortisol 10,653nmol/d (<130) and elevated ACTH 58pmol/L (1.6-3.9).
The patient was commenced on cortisol blocking therapy with metyrapone, however treatment was complicated by urosepsis requiring hydrocortisone replacement. He was then switched to ketoconazole with limited effect despite appropriate dose escalation.
At this time, there was a discussion between the treating oncologist and endocrinologist about alternative treatment options. A novel agent for treatment was put forth and forms the basis of discussion for this case.