Who Is Myo-Inositol For? And Who Should Stay Away From It?

Myo-inositol is one of the most widely advertised and used over-the-counter supplements in female infertility. Yet, as we on previous occasions have pointed out in the VOICE, it is, unfortunately, frequently used inappropriately. Widely advertised by manufacturers as “supportive of healthy ovarian function,” there is, indeed, really little evidence in the literature for such a statement.

Myo-inositol may help IVF patients with PCOS

A review of the literature offers a very different picture: The reality is that absolutely no credible evidence exists that myo-inositol in general improves ovarian function. There is, however, moderate evidence that this supplement may have beneficial effects on IVF outcomes in women with classical polycystic ovary syndrome (PCOS). This, of course, means that myo-inositol should not be used by every female trying to conceive but only by women with classical PCOS phenotype.

Women with low androgens shouldn't take myo-inositol

Why is this such an important conclusion? Because for many infertile women, supplementation with myo-inositol is, indeed, contraindicated. The supplement industry, of course, does not want to tell you that because the industry’s interest is to sell to the widest possible market. Advertising myo-inositol just to classical PCOS patients with excessively high androgen levels, would offer only a much smaller potential target population.

But it is the ability of myo-inositol to lower testosterone levels that makes this supplement an effective treatment in classical PCOS patients. One recent study demonstrated a testosterone declines of more than 50% after such supplementation (Regidor et al., Horm Med Biol Clin Invest 34(2), March 2, 2018). In hyperandrogenic classical PCOS patient, this supplement, therefore, does, indeed, appear indicated (the recommended dosage in the study was 4,000mg/day).

But hyper-androgenism (high testosterone) is almost exclusively only a problem of classical PCOS patients. In all other infertile patients, myo-inositol will lower androgens from normal into abnormally low levels or in women with premature ovarian aging (POA), also called occult primary ovarian insufficiency (oPOI), and women with hypo-androgenic PCOS-like phenotypes (H-PCOS), both already based on their diagnoses hypo-androgenic, supplementing such patients will lower already low testosterone levels even further. And since ovaries need good androgen levels in order to produce good egg numbers and good egg quality, administration of myo-inositol in such patients will achieve exactly the opposite effects on ovaries as desired.

Myo-inositol and DHEA have opposite effects

Aggressive campaigns by various myo-inositol manufacturers and, often, lack of information on the effects of various supplements on female infertility by colleagues, have recently led to a rapidly growing number of female patients coming to CHR who at the same time are taking supplements that oppose each other in their respective functions and, therefore, outweigh each other in their effect on ovaries. The best example are women with POA/oPOI and H-PCOS who, now, by many IVF centers are increasingly supplemented with androgens (often dehydroepiandrosterone, DHEA); yet, at the same time, were advised to initiate supplementation with myo-inositol. DHEA and myo-inositol, of course, make absolutely no sense together in the same patient because DHEA is supplemented to increase testosterone levels in ovaries, while myo-inositol is given to reduce the same. Beware!

This is a part of the February 2020 issue of CHR VOICE.