A 16-year-old girl diagnosed with anorexia nervosa is brought to the emergency department after becoming very light-headed, breaking into a sweat, and developing palpitations while exercising. She exercises regularly. Her serum glucose is 40 mg/dL. The patient is given a soft drink to sip, and she feels better half an hour later. 
Which of the following hormones most likely triggered the sweating and palpitations the patient experienced?
ACTH
Calcitonin
Epinephrine
Insulin