What do D cells secrete?

Answer 1

D-cells, or Delta cells, can be found in the stomach, intestine, or Islets of Langerhans (the hormone producing regions of the pancreas which also produce glucagon and insulin). Delta cells produce somatostatin, a regulatory hormone. When somatostatin is released it interacts with specialized receptor cells, these cells control the production of other hormones. Somatostatin coming in contact with a somatostatin receptor will inhibit the production of hormones that receptor controls.

Answer 2

D cells in the gastrointestinal tract secrete somatostatin, a hormone that inhibits the release of other hormones such as gastrin and insulin. Somatostatin helps to regulate the functions of the digestive system by slowing down processes such as gastric emptying and intestinal motility.