Epsilon cells produce ghrelin and are a fifth, recently discovered, endocrine cell type which reside in the pancreatic Islets of Langerhans. A recent work showed that Neurog3 expression is crucial for epsilon cell development, implying a shared developmental pathway with the four other endocrine cells.
The ghrelin cells are equally distributed in all parts of the pancreas, and on a micro-anatomical location are usually found at the peripheral rim of the islets. In fetal and neonatal islets, they occasionally form a continuous layer embracing the other islet cells.
A few ghrelin-positive cells have been reportedly detected in the duct epithelium or as single, extra-islet cells dispersed among exocrine cells.
In the week 15-26 fetus, ghrelin cells constitute approximately 10% of the islet cells, but following birth, their relative numbers decrease to only 1% of islet cells in adults.