Opioid-Induced Hypogonadism — RACP Adult Medicine MCQ

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ModerateGeneral Internal MedicineOpioid-Induced HypogonadismRACP Adult Medicine

A 50-year-old man with chronic pain on long-term oxycodone 40 mg BD develops constipation, sweating, and hypogonadism. His morning testosterone is 5 nmol/L (low). What is the underlying mechanism of opioid-induced endocrinopathy?

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Correct answer: B — Central suppression of GnRH at the hypothalamus

Opioid-induced endocrinopathy (OIE) affects up to 90% of men on long-term opioids. The primary mechanism is central suppression of GnRH secretion at the hypothalamus, leading to secondary (hypogonadotropic) hypogonadism. This results in low testosterone, low LH/FSH, decreased libido, erectile dysfunction, fatigue, osteoporosis, and depression. Management includes opioid dose reduction/cessation if possible, or testosterone replacement if opioid use must continue.

Reference: AMH – 2025 – Opioid Adverse Effects; eTG – 2025 – Endocrinology