Some neurotransmitters are secreted and released in a similar fashion to peptide hormones, and some 'neuropeptides' may be used as neurotransmitters in the nervous system in addition to acting as hormones when released into the blood.
Algúns neurotransmisores son segregados e liberados de modo similar ao das hormonas peptídicas, e algúns 'neuropéptidos' poden utilizarse como neurotransmisores do sistema nervioso ademais de actuar como hormonas cando se liberan no sangue.