Serotonin (5-HT)
Tryptophan derivative
Serotonin (5-hydroxytryptamine, 5-HT) is synthesised from tryptophan by hydroxylation and decarboxylation. The majority of 5-HT is degraded into 5-hydroxyindoleacetic acid (5-HIAA).
Serotonin is secreted by carcinoid tumours, and in some cases up to 50% of dietary tryptophan (rather than the usual 1%) may be diverted into serotonin synthesis. This may precipitate symptoms of tryptophan deficiency, ie pellagra (dermatitis, dementia, and diarrhoea)
Tyrosine ----> DOPA by tyrosine hydroxylase + THB (Tetrahydrobiopterin)
DOPA ----> Dopamine by DOPA decarboxylase + B6
Dopamine ---> Norepinephrine requires Cu2+ and Vit. C
Norepinephrine ---> Epinephrine by SAM
Tyrosine derivatives
Thyroxine = 2x tyrosine + 3 or 4 iodines (hence T3 and T4)