Serotonin is converted into melatonin, an important hormone in the regulation of sleep, which plays a powerful role in metabolism as well. Serotonin is also the product of an important metabolic pathway, the kynurenine pathway, that involves the fate of the amino acid tryptophan. When people eat protein that contains tryptophan, it has many possible fates. Two important ones are getting converted into serotonin or kynurenine.
