Endocrine Abstracts

Cushing’s syndrome secondary to an ectopic ACTH producing tumour is relatively rare, accounting for approximately 10-20% of cases^[1]. Usually, the primary tumour is bronchial carcinoid or pancreatic neuroendocrine neoplasia^[2]. Prostrate carcinoma is emerging as rare cause of ectopic ACTH production, either as a small cell primary tumour or neuroendocrine differentiation into a small cell type at primary or metastatic sites, post hormonal treatment^[4,5]. It is associated with lower PSA levels than are seen in pure adenocarcinoma and often runs an aggressive clinical course with a poor prognosis. In the literature, fewer than fifty cases of prostrate carcinoma associated with ectopic CS have been documented^[3]. Here, we describe a case in which Cushing’s syndrome was associated with advanced prostate cancer. A 62-year-old gentleman, with a background of prostate adenocarcinoma- pulmonary and hepatic metastases, treated with LHRH agonist + enzalutamide, presented with haematuria. During his admission, profound hypokalaemia (2.3mmol/l) was noted. In the absence of gastrointestinal losses, renal losses of potassium/phosphate was considered and confirmed. Given the atypical spread of his primary malignancy, the low PSA level and refractory hypokalaemia, a neuroendocrine cause was considered. Subsequent workup revealed ACTH-dependent hypercortisolism (cortisol 3182nmol/l; ACTH 262 ng/l). It was noteworthy that patient did not have typical cushingoid phenotype but on initiation of metyrapone, there was rapid resolution of the hypokalaemia. Liver biopsy confirmed neuroendocrine tumour of small-cell type with high Ki-67 index (70%).Although patient was scheduled to receive chemotherapy, he died within 2 weeks of this diagnosis. The case highlights an atypical presentation of Cushing’s, secondary to ectopic ACTH production in the setting of neuroendocrine differentiation of advanced prostate cancer. Acute refractory hypokalaemia, low PSA levels and atypical metastatic spread (pulmonary), are important indicators to consider. The clinical course can be rapidly aggressive, with an associated poor prognosis.