Tryptophan metabolism in embryo implantation and decidualization.

Tryptophan is an essential amino acid for the human body and is crucial for protein synthesis. It is primarily metabolized through the kynurenine, 5-hydroxytryptamine, and indole pathways. The various bioactive compounds produced through tryptophan metabolism can regulate a range of physiological functions, including digestive, metabolic, immune responses, and neurological functions. New evidence supports a close relationship between tryptophan metabolism and embryo implantation; the levels or ratios of tryptophan metabolites, such as kynurenine, serotonin, and melatonin, significantly correlate with various decidualization markers. In this review, we summarize the latest research progress on tryptophan and its metabolites in embryo implantation and their effects on decidualization. Exploring the mechanisms linking tryptophan metabolism to embryo implantation and decidualization may pave the way for novel treatments for reproductive disorders.