Preoperative diagnosis of acromegaly by growth hormone-releasing factor radioimmunoassay

Acromegaly was diagnosed in a 37-year-old woman with classical physical and biochemical findings; an enlarged sella on computed tomography suggested the presence of a pituitary macroadenoma. Radiologic evidence of a lung mass prompted radioimmunoassay of plasma growth hormone-releasing factor (7,500 pg/ml; normal less than 100 pg/ml). After resection of a bronchial carcinoid, which stained positive for growth hormone-releasing factor, circulating growth hormone-releasing factor levels normalized. Subsequently, her clinical, biochemical, and radiologic evidence for acromegaly resolved. This case represents the first reported use of the human pancreatic growth hormone-releasing factor 1-40 radioimmunoassay to preoperatively diagnose this rare etiology of acromegaly.