Supplementation of Myo Inositol & D-Chiro Inositol and its Therapeutic Potential for PCOS
Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women of reproductive age. A complex condition, PCOS is mainly characterized by irregular menstrual cycles, infertility and clinical symptoms of hyperandrogenism. 
Increasing research evidence supports insulin resistance, typically observed in women with PCOS, as the link between the cardiometabolic and reproductive disorders of PCOS.  Oral contraceptives and other medications are also used for the management of hyperandrogenism and ovulation. These medications, however, focus on a single aspect of PCOS pathophysiology and often come with side effects. 
The supplementation of inositol isomers, particularly the combination of Myo Inositol (MI) and D-Chiro Inositol (DCI), show a promising treatment alternative to improve symptoms of PCOS. [2, 3, 5]
Remember to talk with your primary care doctor before starting any supplements, especially if taking other medications.
What are Myo Inositol and D-Chiro Inositol?
Organic compounds found widely in nature, inositols are part of the cell membrane and act as second messengers for different hormones.  As part of the inositol family, MI and DCI are molecules that act as insulin mediators. Although each with specific roles, both are synergistically involved in processes that increase insulin sensitivity in tissues  and in the metabolism of glucose. 
Each type of tissue maintains a specific MI/DCI ratio. This ratio becomes altered when tissues are in a diseased state, such as with insulin resistance.  This inositol imbalance has been observed in women with PCOS.  Thus, it’s hypothesized that MI and DCI supplementation can restore that balance and may provide therapeutic benefits and improvement of PCOS symptoms. 
Insulin Resistance and its Central Role in PCOS
Insulin resistance is a condition in which cells of the body do not respond to insulin (loses sensitivity), thus requiring a higher quantity to achieve expected results.  This situation causes compensatory hyperinsulinemia, which is characterized by elevated levels of circulating insulin. Hyperinsulinemia sets off a series of cellular pathways that ultimately lead to increased concentrations of the hormone androgen (hyperandrogenism). 
Consequently, hyperandrogenism promotes the overproduction of luteinizing hormone (LH), which has been shown to impair ovarian function such as damaging oocyte quality, having menstrual irregularity, and anovulation. 
Insulin resistance also contributes to other cardiovascular risk factors such as dyslipidemia, atherosclerosis, inflammation, and oxidative stress.  Often seen in women with PCOS, these early markers indicate increased risk of cardiovascular diseases.
How Effective are Myo Inositol and D-Chiro Inositol?
As insulin mediators, MI and DCI are involved in increasing insulin sensitivity, thus alleviating insulin resistance.  Correcting insulin resistance then reduces circulating insulin and androgen,  preventing the domino-style effects that ultimately manifest as symptoms of PCOS, as described above. 
Numerous studies have shown the effectiveness of MI and DCI supplementation, particularly in combination.
In one study, the combined therapy of MI + DCI was found to significantly (1) rebalance endocrine profiles (lowering related hormonal levels) and metabolic profiles (lowering insulin, glucose levels) and (2) improve ovulation capability in women with PCOS.  No relevant changes were observed in the placebo group. It describes that DCI mainly effects insulin sensitivity and that MI exerts its effects on numerous ovarian functions, thus combination therapy would be most beneficial. 
Further, a randomized controlled trial found that combined therapy was more effective in improving endocrine, ovulation, and metabolic parameters in women with PCOS than isolated MI treatment.  The combined treatment improved these parameters three months earlier than MI treatment alone. Unlike other current medications used to treat PCOS, the inositol supplementation also reported with no major side effects. 
Another study found that combined supplementation improved lipid profiles in PCOS patients and reduced the risk factors associated with cardiovascular diseases. 
A research review of several studies noted that the combined inositol therapy has potential to improve all symptoms and lab abnormalities of PCOS due to its effect on insulin resistance, compared with other therapies that treat only one aspect of PCOS. 
 Januszewski, M., Issat, T., Jakimiuk, A. A., Santor-Zaczynska, M., & Jakimiuk, A. J. (2019). Metabolic and hormonal effects of a combined myo-inositol and d-chiro-inositol therapy on patients with polycystic ovary syndrome (PCOS). Ginekologia Polska, 90(1), 7-10. DOI: 10.5603/GP.2019.0002
 Troisi, J., Cinque, C., Giugliano, L., Symes, S., Richards, S., Adair, D., Cavallo, P., Sarno, L., Scala, G., Caiazza, M., & Guida, M. (2019). Metabolomic change due to combined treatment with myo-inositol, d-chiro-inositol and glucomannan in polycystic ovarian syndrome patients: a pilot study. Journal of Ovarian Research, 12(25). DOI: https://doi.org/10.1186/s13048-019-0500-x
 Nordio, M., & Proietti, E. (2012). The combined therapy with myo-inositol and d-chiro-inositol reduces the risk of metabolic disease in PCOS overweight patients compared to myo-inositol supplementation alone. European Review for Medical and Pharmacological Services, 16, 575-581. Retrieved from https://www.europeanreview.org/wp/wp-content/uploads/1357.pdf
 Kalra, B., Kalra, S., & Sharma, J. (2016). The inositols and polycystic ovary syndrome. Indian Journal of Ednocrinology and Metabolism, 20(5), 720-724. DOI: 10.4103/2230-8210.189231
 Benelli, E., Del Ghianda, S., Di Cosmo, C., & Tonacchera, M. (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. DOI: http://dx.doi.org/10.1155/2016/3204083
 Sortino, M. A., Salomone, S., Carruba, M. O., & Drago, F. (2017). Polycystic ovary syndrome: insights into the therapeutic approach with inositols. Journal Frontiers in Pharmacology, 8(341), 1-13. DOI: 10.3389/fphar.2017.00341
 Minozzi, M., Nordio, M., & Pajalich, R. (2013). The combined therapy myo-inositol plus d-chiro inositol, in a physiological ratio, reduces the cardiovascular risk by improving the lipid profile in PCOS patients. European Review for Medical and Pharmacological Sciences, 17(4), 537-540. Retrieved from https://www.europeanreview.org/article/3314