We describe a 55-year-old female who presented with a 1-year history of tiredness, depression and painful stiff joints. The most striking clinical abnormality was bilateral frozen shoulders, local corticosteroid treatment of which provided the first diagnostic clue. She was found to have profound diminution of plasma cortisol secondary to an isolated deficiency of ACTH. There was no obvious cause for this. Steroid replacement eradicated her lethargy within 3 months and evidence of frozen shoulders resolved completely.