Unfer, V., Facchinetti, F., Orrù, B., Giordani, B., & Nestler, J. (2017). Myo-inositol effects in women with PCOS: a meta-analysis of randomized controlled trials. Endocrine connections. https://doi.org/10.1530/EC-17-0243
Unfer V, Facchinetti F, Orrù B, Giordani B, Nestler J. Myo-inositol effects in women with PCOS: a meta-analysis of randomized controlled trials. Endocrine connections. 2017. doi:10.1530/EC-17-0243
Unfer, Vittorio, et al. "Myo-inositol effects in women with PCOS: a meta-analysis of randomized controlled trials." Endocrine connections, 2017.
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Myo-inositol lowers fasting insulin in women with PCOS
A meta-analysis of nine randomized trials found that women with PCOS who took myo-inositol had lower fasting insulin and less insulin resistance than comparison groups. The trials enrolled 247 women taking myo-inositol and 249 in comparison groups. Testosterone showed a slight downward trend that was not significant.
Key Findings
Nine randomized trials were pooled: 247 women received myo-inositol, alone or with d-chiro-inositol, and 249 women received folic acid or other treatments.
Fasting insulin fell with myo-inositol (SMD = −1.021, 95% CI: −1.791 to −0.251, P = 0.009) across seven trials, with heterogeneity of I2 = 90.6%.
The HOMA index, a calculated measure of insulin resistance, also fell (SMD = −0.585, 95% CI: −1.145 to −0.025, P = 0.041).
Androstenedione was unaffected, and testosterone showed a slight downward trend that did not reach significance (P = 0.097).
Serum SHBG rose significantly only in the trials where myo-inositol continued for 24 weeks (P = 0.026), and not in trials lasting up to 16 weeks.
Interpretation
The authors pooled randomized controlled trials and added a trial sequential analysis, and report that the insulin result crossed the threshold for firm evidence after the fourth trial. Comparison groups varied: folic acid, d-chiro-inositol and contraceptive pills. The trials also differed in how they defined PCOS and in treatment length, and the authors attribute the high heterogeneity to these differences. Two authors work for a supplement manufacturer, and a third was paid as a consultant for the analysis. Outcomes were blood markers.
RRM Context
Restorative reproductive medicine looks for the cause of irregular ovulation. Insulin resistance is a leading cause in PCOS, and the review reports it in 50–70% of women with the condition. PCOS now also carries the name PMOS (Polyendocrine Metabolic Ovarian Syndrome). Cause-based care pairs metabolic care with cycle charting. The authors cite another meta-analysis showing that inositol helps promote ovulation in PCOS.
Our editorial summary of this paper, not the article's abstract.
Abstract
Myo-inositol (MI) supplementation in women with polycystic ovary syndrome (PCOS) has been evaluated over the last years. Many hormonal and reproductive impairments associated with this disorder seem relieved by the supplement. The objective of the meta-analysis was to assess the effects of MI alone or combined with d-chiro-inositol (DCI) on the endocrine and metabolic abnormalities of women with PCOS. Literature was retrieved from selected databases, MEDLINE, EMBASE, PubMed and Research Gate (up to November 2016). Only randomized controlled trials (RCTs) investigating the effects of MI alone or combined with DCI were reviewed. Nine RCTs involving 247 cases and 249 controls were included. Significant decreases in fasting insulin (SMD = -1.021 µU/mL, 95% CI: -1.791 to -0.251, P = 0.009) and homeostasis model assessment (HOMA) index (SMD = -0.585, 95% CI: -1.145 to -0.025, P = 0.041) were identified after MI supplementation. The trial sequential analysis of insulin meta-analysis illustrates that the cumulative z-curve crossed the monitoring boundary, providing firm evidence of the intervention effect. A slight trend toward a reduction of testosterone concentration by MI with respect to controls was found (SMD = -0.49, 95% CI: -1.072 to 0.092, P = 0.099), whereas androstenedione levels remained unaffected. Throughout a subgroup's meta-analysis, a significant increase in serum SHBG was observed only in those studies where MI was administered for at least 24 weeks (SMD = 0.425 nmol/L, 95% CI: 0.050-0.801, P = 0.026). These results highlight the beneficial effect of MI in improving the metabolic profile of women with PCOS, concomitantly reducing their hyperandrogenism.
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