Endocrine Abstracts

Ectopic adrenocorticotropic hormone (ACTH) syndrome occurs in about 5–10% of all patients with ACTH-dependent hypercortisolism. We present the case of a 35 year old gentleman who presented with a six month history of progressive 16 kg weight gain and breathlessness. Pulmonary imaging revealed bilateral infiltrates suspicious for Pneumocystis pneumonia (PCP). Physical examination was concerning for Cushing’s syndrome, with facial plethora, easy bruisability and broad violaceous striae on his abdomen and thighs. Initial laboratory testing showed a profound hypokalemia (serum potassium 2.3 mmol/l (3.5–4.5 mmol/l). Endogenous hypercortisolaemia was confirmed with an overnight dexamethasone supression (ONDS) cortisol of 656 nmol/l. 24 h Urine Free Cortisol (UFC) was raised at 853 nmol/24 h. ACTH was elevated at 167 (72–63.3 pg/ml). The remainder of his pituitary profile was unremarkable with the exception of a testosterone of 3.0 (8.6–29 nmol/l). Ectopic ACTH was confirmed with Corticotroph Releasing Factor (CRF) testing failing to show a satisfactory rise in ACTH (147–175 pg/ml; 19%). Bilateral inferior petrosal sinus sampling (BIPSS) did not show a peripheral ACTH gradient and magnetic resonance imaging (MRI) pituitary was negative for an adenoma. Computed tomography of the thorax, abdomen and pelvis (CT-TAP) and Octreotide scintigraphy did not identify a culprit lesion. Calcitonin and urinary 5-Hydroxyindoleacetic acid (5-HIAA) levels were normal. His cortisol levels responded to Metyrapone with addition of Hydrocortisone to prevent adrenal insufficiency. His PCP was successfully treated with a course of co-trimoxazole. The clinical course was complicated by an admission with decompensation of congestive cardiac failure secondary to Cushing’s cardiomyopathy. He is currently awaiting a 68Ga-DOTA-TATE PET/CT in the hope of localizing the ectopic ACTH-secreting tumour. This case highlights the profoundly immunocompromised state of severe Cushing’s syndrome and the diagnostic challenge in localizing the offending lesion in ectopic ACTH.