Identify the function of each hormone listed in the options to understand their roles in the body.
Thyroxine is a hormone produced by the thyroid gland, primarily involved in regulating metabolism.
Adrenaline, also known as epinephrine, is produced by the adrenal glands and is involved in the body's fight-or-flight response.
Insulin is produced by the pancreas and plays a crucial role in regulating blood glucose levels.
Gastrin is a hormone produced by the stomach lining that stimulates the secretion of gastric acid, aiding in digestion. Therefore, it is the hormone produced by the digestive tract.