Myo-Inositol and Its Derivatives: Their Roles in the Challenges of Infertility.

Myo-inositol (MYO) and D-chiro-inositol (DCI) are the two most significant isomeric forms of inositol, playing a critical role in intracellular signaling. MYO is the most abundant form of inositol in nature; DCI is produced from MYO through epimerization by an insulin-dependent enzyme. Recently, it has been demonstrated that inositol may influence oocyte maturation and improve intracellular Ca2+ oscillation in the oocytes, and it has been proposed as a potential intervention for restoring spontaneous ovulation. The MYO concentration in human follicular fluid is considered a bioindicator of oocyte quality. In the ovary, DCI modulates the activity of aromatase, thus regulating androgen synthesis. Under physiological conditions, the MYO/DCI ratio is maintained at 40:1 in plasma. In women with PCOS, the MYO/DCI ratio is lowered to 0:2:1, contributing to elevated androgen production. By regulating FSH signaling, MYO administration increases the number of high-quality embryos available for transfer in poor responder patients. Finally, by acting downstream to insulin signaling, inositol administration during pregnancy may represent a novel strategy for counteracting gestational diabetes. These findings show that diet supplementation with inositol may be a promising strategy to address female infertility and sustain a healthy pregnancy.