Myo-Inositol: Evidence-Based Support for Women with PCOS and Insulin Resistance

Myo-inositol is a naturally occurring cyclic carbohydrate, once thought to be vitamin B8. Although not considered essential, it plays a key role in glucose metabolism and is produced endogenously, particularly by the kidneys. It is found in high concentrations in tissues that utilise large amounts of glucose such as the brain, heart, and ovaries ^[1][2][3][7].

The demand for myo-inositol increases with age, high sugar intake, sodium deficiency, insulin resistance, antibiotic use, and conditions like type 1 and type 2 diabetes ^[5][6]. Folate, on the other hand, is critical for DNA synthesis and repair, and plays a synergistic role in reproductive health.

Myo-Inositol and PCOS

Insulin resistance is present in 70–80% of women with PCOS and central obesity and 15–20% of lean PCOS patients ^[8]. Hyperinsulinemia contributes to androgen excess and disrupted ovulation through elevated LH secretion. Myo-inositol has shown positive effects in modulating these mechanisms:

• In a 12-week RCT, 2g of myo-inositol (plus 200mcg folate) significantly reduced LH, prolactin, testosterone, insulin, and the LH:FSH ratio, while restoring menstrual cycles in amenorrheic/oligomenorrheic women ^[9].
• Another study found 2g/day improved ovulation, insulin resistance, and reduced BMI in anovulatory PCOS patients. 61.7% ovulated with myo-inositol, and 72.2% with added clomiphene ^[10].

Myo-Inositol vs. Metformin

Although metformin is a common treatment for PCOS, studies show that myo-inositol is better tolerated with fewer side effects, while still offering metabolic and reproductive benefits ^[11].

IVF Support Beyond PCOS

A systematic review found that myo-inositol supplementation reduced gonadotropin requirements in both PCOS and non-PCOS women undergoing IVF. It also significantly shortened ovarian stimulation in the PCOS group ^[12].

In PCOS patients, an imbalance between myo-inositol and D-chiro-inositol (DCI) in the ovaries contributes to dysfunction. High conversion of myo-inositol to DCI may reduce oocyte quality and follicular function ^[13].

Gestational Diabetes Prevention

Two separate trials demonstrated that taking 2g of myo-inositol twice daily reduced the incidence of gestational diabetes by 65–87.3% in high-risk pregnancies ^[14][15].

Myo-inositol combined with folate supports insulin sensitivity, hormonal balance, ovulation, and pregnancy outcomes in women with PCOS and insulin resistance. It also offers added benefits for IVF patients and in gestational diabetes prevention.

References

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11. Unfer V et al. (2014). Reprod Sci;21:854–8.
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13. Matarrelli B et al. (2013). J Matern Fetal Neonatal Med;26:967–72.