serotonin

/ˌsɛɹəˈtəʊnɪn/

IPA: /S ER0 AH0 T OW1 N IH0 N/

noun
  1. 1

    An indoleamine neurotransmitter, 5-hydroxytryptamine, that is involved in depression, appetite, etc., and is crucial in maintaining a sense of well-being, security, etc.

Source: https://en.wiktionary.org/wiki/serotonin