Which of the following substances is NOT classified as a hormone?

Pancreatin is not classified as a hormone, which makes it the correct choice in this context. Pancreatin is an enzyme mixture derived from the pancreas, primarily containing digestive enzymes such as amylase, lipase, and proteases. These enzymes are crucial for the digestion of carbohydrates, fats, and proteins in the gastrointestinal tract, but they do not function as hormones, which are chemical messengers that regulate physiological processes in the body.

In contrast, cortisol is a hormone produced by the adrenal glands that plays a significant role in the body’s stress response, metabolism, and immune function. Insulin is a hormone produced by the pancreas that regulates blood glucose levels. Thyroxine, or T4, is a hormone secreted by the thyroid gland that regulates metabolism and energy production in the body. Each of these substances has a specific role in hormonal signaling, separate from the enzymatic functions of pancreatin.