Final answer:
Estrogen is not primarily identified as affecting appetite and food intake; it is more involved in reproductive functions. Cholecystokinin (CCK), glucagon, and insulin are recognized for their roles in regulating appetite, satiety, and energy metabolism.
Step-by-step explanation:
Hormones play a crucial role in regulating appetite and food intake. Among the hormones listed, estrogen, glucagon, and insulin are all recognized for affecting appetite and energy metabolism. However, estrogen is not primarily identified as affecting appetite and food intake in the context of digestion. Rather, it is more involved in reproductive functions and can influence body weight in that context but is not a direct regulator of eating behavior on a meal-to-meal basis like the other hormones listed. Hormones like cholecystokinin (CCK), which is secreted in response to the ingestion of fat or protein, signals satiety and reduces food intake. Glucagon, which is produced by the pancreas along with insulin, works to increase blood glucose levels, and plays a role in signaling hunger. Insulin is secreted after food intake and facilitates the uptake of glucose from the blood into cells, thus also playing a role in signaling satiety.