Recently, attention has been given to the role of inositol–phosphoglycan (IPG) mediators in insulin action. Molecular and animal studies showed that D-chiro-inositol deficiency and an imbalance with its precursor myoinositol (MYO) are directly related to the insulin resistance. In particular, the stereoisomer MYO is an important constituent of the follicular microenvironment, where it seems to play an important role in both nuclear and cytoplasmic oocyte development. It was demonstrated that in human follicular fluids, higher concentrations of MYO are related to a better quality of oocytes.
Some authors have experimented with MYO supplementation in both obese and lean PCOS patients, reporting varying degrees of improvement in clinical, hormonal and metabolic features of the syndrome. However, previous reports in PCOS subjects exclusively evaluated the clinical effects of formulations containing MYO plus folic acid. In addition, no direct comparisons with other insulin sensitizing compounds, regarding the effects on clinical and biochemical characteristics of the syndrome, are available in literature. The only published study comparing MYO and metformin focused on the ovulation and pregnancy rates in a population of infertile PCOS women.