Measurement of gut hormones in plasma

The gastrointestinal tract is the largest endocrine organ and was the site where the first hormones were discovered: secretin in 1902 and gastrin in 1905. Discovery of these gut peptides led to the concept of blood-borne communication between cells. Gut peptide hormones and neurotransmitters regulate the complex processes of digestion, motility, epithelial growth, and integrity. Investigation of this complex endocrine organ has depended on the development of well-characterized radioimmunoassays. Radioimmunoassays have increased our understanding of appetite regulation and of pathological processes affecting the gut, including gastroenteropancreatic neuroendocrine tumors. The object of this chapter is to provide an overview of measuring gastrointestinal hormones and neuropeptides by radioimmunoassay.