Module IV: Gastroenterology focuses on comprehensive metabolic, functional, and nutritional approaches to gastrointestinal dysfunction and disease. Findings indicate that 70 percent of the immune system is located in the GI tract, while 90 percent of serotonin is created in the GI tract—along with other nutrients. If the gut microbiome is dysregulated or dysfunctional, the patient cannot achieve optimal health. This module explores new therapies available to enhance GI health, along with celiac disease and gluten sensitivity, the gut-immune-brain connection, irritable bowel syndrome, hormones and diet, and other digestive and glandular disorders.