Pituitary gastrins occur in corticotrophs and melanotrophs.

The gut hormone gastrin was identified in pituitary cells containing adrenocorticotropic hormone and alpha-melanocyte--stimulating hormone by region-specific immunocytochemistry and radioimmunoassay. Smaller amounts of gastrin were found in nerve fibers of the neural lobe and pituitary stalk. Since adrenocorticotropic hormone--like peptides occur in antropyloric gastrin cells, these data indicate a considerable similarity in peptide composition of pituitary and gastrointestinal endocrine cells and reinforces questions of multiple hormone production.