ABSTRACT
Abiraterone acetate causes an adrenocorticotropic hormone (ACTH)-mediated mineralocorticoid excess. We present a 77-year-old man with prostate adenocarcinoma who developed signs and symptoms of mineralocorticoid excess while on abiraterone and discuss its pathophysiology and treatment options. The patient developed hypokalemia, metabolic alkalosis, and hypertension, indicative of increased mineralocorticoid activity, confirmed by elevated ACTH, corticosterone, and deoxycorticosterone levels. Abiraterone inhibits cytochrome P450c17 (CYP17A1), thus inhibiting testosterone and cortisol synthesis. Diminished cortisol synthesis, in turn, leads to excessive mineralocorticoid precursor production mediated by ACTH, leading to enhanced sodium absorption and potassium excretion. Abiraterone is often prescribed with low-dose prednisone to suppress ACTH; however, this strategy may not provide physiological glucocorticoid levels, resulting in ACTH-mediated mineralocorticoid excess in some patients. High-dose steroids or mineralocorticoid antagonists may activate mutant androgen receptors in prostate cancer tissue; therefore, amiloride is suggested for managing residual mineralocorticoid activity. This case highlights the importance of being vigilant for the signs and symptoms of mineralocorticoid excess in patients on abiraterone.