Serotonin rhymes with:
melatonin, melatonin, seratonin, bonin, cronin, melatonin, ronin, seratonin, antonin, behunin, benin, bonin, bonnin, bradykinin, branin, canin, chanin, chernin, clanin, clendenin, cronin, dennin, dobrynin, dornan, dornin, dubinin, durnin, fannin, henin, jenin, junine, kunin, lignin, magnin, melatonin, monnin, pankonin, ronin, runnin', seratonin, simonin, tinnin, wolanin
Serotonin sounds like:
sardina, sardine, sardinha, sardinia, sartain, sartin, scardina, scardino, sciortino, scrotten, scrutiny, scruton, scrutton, secretion, seratonin, sheraton, sheridan, shorten, sordoni, sortino, srdan