We describe here the case of a 45-year-old man with a chronic history of heroin abuse who has received methadone maintenance therapy for 12 years. At admission, on this occasion, for stabilisation on methadone, he reported a two-year history of painful gynaecomastia and testicular atrophy. Investigations revealed abnormal sex hormone levels. Liver function tests, thyroid function tests, Brain (pituitary) MRI and viral screens were normal. Following assessment and abnormality in two morning total testosterone level measurements he was diagnosed with hypogonadism secondary to opioid use. Although he had a previous history of alcohol abuse, he was abstinent from alcohol use for five years at time of assessment. He was commenced on parenteral testosterone replacement with therapeutic benefit. In light of the increased use of opioids, it is important to recognise and manage the endocrine complications of opioid use. The need for an empathic and adequate sexual history, physical examination and investigation is essential in patients who use opioids to ensure that cases of hormonal dysfunction are detected early and managed appropriately.