text: is serotonin a hormone? have to give a presentation on the endocrine system.  must choose a hormone.  i know that serotonin is a neurotransmitter but i don't know if it is an actual hormone. serotonin (5-hydroxytryptamine, or 5-ht) is a monoamine neurotransmitter synthesised in serotonergic neurons in the central nervous system and enterochromaffin cells in the gastrointestinal tract.  in the central nervous system, serotonin is believed to play an important role in the regulation of mood, sleep, emesis (vomiting), sexuality and appetite. serotonin has been thought to play a part in many disorders, notably as part of the biochemistry of depression, migraine, bipolar disorder and anxiety.  the name "serotonin" is something of a misnomer and reflects the circumstances of the compound's discovery. it was initially identified as a vasoconstrictor substance in blood serum - hence serotonin, a serum agent affecting vascular tone. this agent was later chemically identified as 5-hydroxytryptamine (5-ht), and, as the broad range of physiological roles were elucidated, 5-ht became the preferred name in the pharmacological field.