Gonadotropin-releasing hormone agonists, used widely in the treatment of metastatic prostate cancer and hormone receptor-positive breast cancer, are associated with a rare but potentially fatal outcome of pituitary apoplexy (PA). An 85-year-old man presented with sudden onset of headache, left eye pain, sensitivity to light, nausea and vomiting. The symptoms started 4 hours after initiation of leuprolide therapy for treatment of recently diagnosed metastatic prostate carcinoma. Radiological imaging of the brain demonstrated a heterogeneously enlarged pituitary gland measuring 19×16×13 mm and T1-hyperintense signal compatible with pituitary haemorrhage. Hormone function tests were indicative of panhypopituitarism, confirming the diagnosis of PA. Due to age, the patient was started on hormonal replacement therapy and eventually symptoms improved.