Conceptualization of Endocrine Function of the Gastrointestinal Tract

The gastrointestinal systems (GIT) and endocrine systems are integrated into a well-coordinated complex to meet the metabolic needs of the body. The endocrine functions and possible dysfunctions are less emphasized in the medical curriculum. Hormones are synthesized and released by different segments of the GIT to perform specific functions. The main sites of synthesis and secretion are the stomach and intestines. The hormones of the GIT are categorized as paracrine, neurocrine, and endocrine.

Cholecystokinin (CCK), gastrin, secretin, glucose-dependent insulinotropic peptide or gastrin inhibitory peptide (GIP), and motilin are Endocrine hormones. Somatostatin and histamine are examples of Paracrine hormones. Enkephalins, vasoactive intestinal peptides (VIP), and gastrin-releasing peptides (GRP) are examples of neurocrine hormones. An additional three work together as paracrine and endocrine hormones Glucagon-like peptide [GLP-1], pancreatic polypeptide, and peptide-YY. Villikinin from Brunner’s gland of the duodenum, duocrinin from intestinal mucosa, and parotin are a few others rarely discussed in most literature. Gastrointestinal tract hormones play crucial roles in providing satiety, maintaining hormonal secretion and inhibition, and breaking down proteins, fats, and carbohydrates into simple molecules for absorption. There are documented manifestations of hypersecretion or hyposecretion of these hormones. Likewise, known medical conditions can subsequently lead to GIT hormone dysfunction.

Gastric Outlet Obstruction, Somastinoma, celiac disease, Zollinger-Ellison Syndrome, Crohn's disease, ulcerative colitis, tropical sprue, intestinal resection, pancreatic insufficiency, gastric ulcers, infective diarrhea, and Inflammatory bowel disease(IBS) are few known documented medical conditions that lead to GIT hormonal dysfunctions. The Article aims to reiterate the endocrine function and dysfunction of the GIT. The review article is part of an integrative learning process for students.