You will be given a definition of a task first, then some input of the task.
In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: The gastrointestinal system releases a peptide hormone that increases during fasting and decreases after ingestion, called:
Options: <1> Leptin <2> Cholecystokinin <3> Ghrelin <4> Insulin. <5> Glycogen
Output:
3