Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder among women of childbearing age, characterized by ovulatory dysfunction, hyperandrogenism, and/or polycystic ovarian morphology, often accompanied by insulin resistance and metabolic abnormalities. Inositol, a naturally occurring sugar alcohol, has emerged as a safe and effective intervention for alleviating PCOS symptoms, with its two main isomers—myo-inositol (MI) and D-chiro-inositol (DCI)—playing key roles in modulating metabolic, hormonal, and reproductive functions in women with PCOS.
The primary mechanism by which inositol improves PCOS is its role as an insulin sensitizer. A large proportion of women with PCOS suffer from insulin resistance, regardless of their body mass index (BMI), which triggers excessive insulin secretion and disrupts the hypothalamic-pituitary-ovarian axis. Inositol, particularly DCI, enhances insulin signaling by participating in the synthesis of phosphoglycan derivatives, thereby reducing insulin resistance and lowering circulating insulin levels. Clinical studies have shown that inositol treatment significantly decreases fasting glucose levels, insulin AUC (area under the curve), and insulin resistance scores, while improving glucose metabolism compared to placebo groups. Unlike metformin—the gold standard insulin sensitizer—inositol is associated with fewer gastrointestinal side effects, making it a more tolerable alternative for many women with PCOS.
In addition to improving insulin sensitivity, inositol exerts direct regulatory effects on ovarian steroidogenesis, addressing the core issue of hyperandrogenism in PCOS.
Another crucial benefit of inositol is its ability to improve reproductive outcomes in women with PCOS. Ovulatory dysfunction is a major cause of infertility in PCOS, and inositol has been shown to enhance ovulation frequency and normalize menstrual cycles. A meta-analysis of 26 randomized controlled trials (RCTs) found that women treated with inositol had a 1.79 times higher risk of having regular menstrual cycles compared to those taking a placebo, with efficacy non-inferior to metformin in this regard. Inositol also accelerates the time to first ovulation and improves follicular maturation, as evidenced by increased circulating estradiol levels in the early stages of treatment.
In terms of metabolic health, inositol contributes to modest improvements in body composition and lipid profiles. Clinical trials have demonstrated that inositol treatment leads to a small but significant reduction in BMI, as well as an increase in high-density lipoprotein (HDL) cholesterol, which helps reduce cardiovascular risk associated with PCOS. However, its metabolic benefits may be less pronounced in morbidly obese women (BMI > 37), highlighting the need for personalized treatment approaches.