A 40-year-old woman develops light-headed episodes associated with sweating, palpitations, and hunger whenever she misses a meal. Her physical examination is normal, and she is not taking any medications. On one such episode, while in hospital, her blood glucose level was 30 mg/dL and the symptoms resolved with giving her juice. Which of the following is the most likely diagnosis?
excess growth hormone Cushing's disease thyrotoxicosis tumor of the pancreatic beta-cells