Enteroendocrine cells are the most abundant hormone producing cells in humans. Though they make up less than 1 % of the gastrointestinal epithelium, these cells have a large physiological impact through the secretion of hormones that act both locally and systemically to regulate intestinal function and whole-body metabolism, among other functions. The differentiation of enteroendocrine cells from intestinal stem cells is complex, involving not only lineage, but hormonal specification. This review highlights the specific signaling pathways and transcription factors that regulate enteroendocrine cell differentiation and hormone production, integrating newer findings into our growing understanding of this process. Further, it also describes how enteroendocrine cells and their differentiation are involved and altered in human health and disease: specifically aging, inflammatory bowel disease, obesity, and diabetes mellitus. Finally, we focus on how enteroendocrine cells can be targeted to produce insulin, a growing field with significant implications. Understanding what drives enteroendocrine differentiation, both molecularly and physiologically, will provide important insights into how these cells can serve as future therapeutic targets.