Definition: 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'.
Input: 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
