Gastro-intestinal hormones. What remains?

Study of gastro-intestinal hormones is a very young science. It's break through came with the isolation and synthesis of pure hormones and in particular with introduction of radio-immunoassay in gastroenterology. Even from clinical viewpoint the practical advances in so short a period of time are considerable. Almost impossible to grasp is the growth of knowledge, which grew in the physiological and technical field from the study of gastro-intestinal hormones.