Abiraterone Mineralocorticoid Excess — RACP Adult Medicine MCQ

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HardMedical OncologyAbiraterone Mineralocorticoid ExcessRACP Adult Medicine

A 65-year-old man with metastatic castration-resistant prostate cancer on abiraterone presents with muscle weakness and hypokalaemia (K+ 2.9 mmol/L). His blood pressure is 165/95 mmHg. What is the mechanism of these adverse effects?

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Correct answer: D — Excess mineralocorticoid activity due to CYP17 inhibition

Abiraterone inhibits CYP17A1, blocking androgen synthesis. However, the upstream ACTH drive leads to accumulation of mineralocorticoid precursors (particularly corticosterone and deoxycorticosterone), causing hypertension, hypokalaemia, and fluid retention. Co-prescription of prednis(ol)one 5 mg BD is mandatory with abiraterone to suppress ACTH and prevent these mineralocorticoid excess effects. Potassium and blood pressure should be monitored regularly.

Reference: AMH – 2025 – Abiraterone; eTG – 2025 – Oncology