Which pancreatic secretion blocks the release of both glucagon and insulin?

1. Delta cells account for about four percent of islet cells and secrete the peptide hormone somatostatin. 2. Pancreatic somatostatin is an inhibiting hormone that blocks release of both glucagon and insulin. 3. The same molecule is released by the hypothalamus as growth hormone inhibiting hormone, and by the stomach and intestines. 4. Pancreatic polypeptide from PP cells is linked to appetite and to pancreatic secretion rather than to blocking these two hormones. 5. Insulin and glucagon are the hormones being blocked, so neither can be the blocker. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 17 "The Endocrine System", section 17.9 The Endocrine Pancreas_