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PCOS & Inositol

Posted by Allie on 30th August 2016

Inositol has been found to help improve PCOS symptoms
Photo: Pixabay.com

Insulin resistance has been found to affect approximately 50-80% of women with PCOS, regardless of their weight (1), and is associated with an increased risk of type 2 diabetes, high blood pressure and cholesterol. It has typically been treated with insulin sensitizing medications, such as metformin. However, research has found that a naturally occurring insulin sensitizer called inositol is also an effective therapeutic option for women with PCOS and can improve symptoms.

What is inositol?

Inositol is assumed to belong to the vitamin B complex but the human body can actually make it on its own. Inositol refers to a group of molecules that share the same structure called stereoisomers. There are 9 stereoisomers of inositol, two of which are currently used to treat PCOS and available as supplements: myo-inositol (MI) and D-chiro-inositol (DCI).

MI is the most abundant form of inositol in humans and is the main focus of this article. MI is also found in foods such as fruits, grains and seeds (2). MI is a precursor of DCI and makes it using specific enzymes. Each tissue in the body, such as muscles and the liver, converts a different amount of MI into DCI depending on its individual needs.

Why is inositol important for women with PCOS?

Both MI and DCI act as insulin second messengers, which means they communicate with cells and increase the insulin sensitivity of tissues to help them perform different ovulatory and metabolic functions (3).

MI and DCI each perform specific actions. DCI plays a role in activating enzymes that metabolise glucose and reduces circulating insulin and androgens (3). MI plays a critical role in the ovary and high levels have been associated with good quality oocytes, which are eggs in the ovaries that have not yet matured. This could be of importance for women with PCOS struggling to get pregnant as poor oocyte quality is a cause of infertility (1).

MI plays a critical role in the ovary and high levels have been associated with good quality [eggs] in the ovary.

Insulin resistance is believed to be a key factor in menstrual irregularity, anovulation, and high levels of androgens in PCOS (3). You can read more about insulin resistance in PCOS here. Exacerbated by obesity, insulin resistance in PCOS is believed to be due to a defect with the following: insulin receptors in cells and the way glucose is transported (4); how inositol is metabolised by the body (4); and/or the release of D-chiro-inositol-containing inositolphosphoglycan mediators, which are second messengers (5).

Therefore, it appears important that women with PCOS have sufficient levels of MI and DCI to manage insulin resistance and symptoms of the condition.

How can inositol supplements help improve PCOS symptoms?

Insulin sensitizing drugs aim to improve insulin resistance, reduce hyperinsulinemia, and re-establish menstruation and ovulation (4). Research looking into the effectiveness of MI in PCOS has found that restoring inositol levels with supplements balances hormonal disturbances by improving the insulin resistance of certain tissues. Researchers have hypothesized that MI supplementation helps reduce levels of insulin and other hormones involved in PCOS, such as testosterone and luteinizing hormone.

Unfer et al (2012) completed a systematic review of randomised controlled trials, considered the ‘gold standard’ of research design, looking into the effects of MI in women with PCOS and the results are summarised below.

Research has found that restoring inositol levels with supplements [improves] the insulin resistance of certain tissues.

Taking a MI supplement has been shown to induce regular menstrual cycles in women with PCOS. Another study found that women with PCOS treated with MI lost weight compared to the placebo group. MI, rather than DCI, supplementation has also been shown to improve oocyte quality and restore ovulation with a slight improvement in pregnancy rates than metformin.

One study examining the benefits of combining MI and DCI in 46 young overweight women with PCOS found that it improved insulin resistance and ovulatory function. Further research into the combined use of inositol stereoisomers is needed with a larger sample of participants however, the results are encouraging.

How much myo-inositol should women with PCOS be taking?

In the studies discussed above, MI doses of both 2g and 4g daily were taken. The authors (4) assert that taking 4g a day is a more complete treatment and helps to treat all PCOS symptoms.

The research examining the effectiveness of MI supplementation in PCOS is very positive. Additionally, it isn’t a pharmaceutical drug and no side effects have been reported in the studies discussed. Before taking supplements to help PCOS symptoms, or if you would like further information, please liaise with a medical professional or relevant healthcare professional to discuss your individual needs.


Note that referenced or mentioned authors, websites and organisations are not affiliated with, nor endorsing, the content published on Positive PCOS.

1: R. Isabella & E. Raffone. 2012. Does ovary need D-chiro-inositol? Journal of Ovarian Research. 5:14

2: A.S. Lagana et al. 2016. Metabolism and Ovarian Function in PCOS Women: A Therapeutic Approach with Inositols. International Journal of Endocrinology. Volume 2016, Article ID 6306410

3: E. Benelli et al. 2016. A Combined Therapy with Myo-Inositol and D-Chiro-Inositol Improves Endocrine Parameters and Insulin Resistance in PCOS Young Overweight Women. International Journal of Endocrinology. Volume 2016, Article ID 3204083

4: V. Unfer et al. 2012. Effects of myo-inositol in women with PCOS: a systematic review of randomized controlled trials. Gynecological Endocrinology. 28(7):509-15

5: J.E. Nestler et al. 2000. Role of inositolphosphoglycan mediators of insulin action in the polycystic ovary syndrome. Journal of Pediatric Endocrinology and Metabolism. 13 (5): 1295-8