Its other name is 5- hydroxytryptamine and is also found in platelets. Release of serotonin by injured platelets is thought to cause blood vessels to contract. We really do not know the triggers for hunger or appetite. It seems that serotonin is involved, but where and how are currently unknown. There is a blood test for serotonin.
Some Psychiatrists use it to indicate the appropriate type of drug to use.
I have been told I have Serotonin syndrome, but I am not sure what that implies. I realize I am unable to take the popular SSRI antidepressants without severe side effects. I notice there is a section on Serotonin syndrome of the FAQ page, but I am denied access. There are several syndromes that could be referred to as Serotonin Syndrome. First is overproduction by carcinoid cells of serotonin.