Tryptophan metabolism: A hidden regulator of female reproductive health beyond fertility.

Female reproductive health encompasses fertility, safe pregnancy and childbirth, and is vital throughout the entire life of women. Tryptophan, an essential amino acid in humans, is involved in protein synthesis and the generation of bioactive substances related to the health and disorders of multiple systems. An increasing number of studies have shown that tryptophan metabolism is closely related to female reproductive health. Tryptophan metabolism occurs mainly through the kynurenine, serotonin, and indole pathways and yields various bioactive substances. The homeostasis of this metabolism modulates the ovarian function by influencing follicle development and hormone secretion. The regulation of the female reproductive system by tryptophan metabolism may be related to its role in the maternal internal environment and its influence on the reproductive axis systemically. In pregnant women, tryptophan metabolism affects the entire process from embryo implantation to childbirth. Factors involved in tryptophan metabolism may represent new targets for the treatment of female reproductive system-related diseases. Here, we summarize the possible mechanisms by which tryptophan metabolites affect female reproductive health and discuss potential related treatments.