Effects of inositol on ovarian function and metabolic factors in women with PCOS: a randomized double blind placebo-controlled trial.

Background: Women with oligomenorrhea and polycystic ovaries show a high incidence of ovulation failure perhaps linked to insulin resistance and related metabolic features. A small number of reports shows that inositol improves ovarian function. Futhermore, in these trials the quality of evidence supporting ovulation is suboptimal, and few studies have been placebo-controlled. The aim of this study was to use a double-blind, placebo-controlled approach with detailed assessment of ovarian activity (two blood samples per week) to assess the validity of this therapeutic approach in this group of women.

Methods: Of the 283 patients randomized, 2 withdrew before treatment commenced, 147 received placebo, and 136 received inositol (100 mg, twice a day). The women which discontined the study prematurely were more numerous in the treatment group (n = 45) than the placebo group (n = 15; P < 0.05).

Results: The ovulation frequency estimated by the ratio of luteal phase weeks to observation weeks was significantly (P < 0.01) higher in the treated group (23%) compared with the placebo (13%). The time in which the first ovulation occurred was significantly (P < 0.05) shorter [23.6 d; 95% confidence interval (CI), 17, 30; compared with 41.8 d; 95% CI, 28, 56]. The number of patients failing to ovulate during the placebo-treatment period was higher (P < 0.05) in the placebo group, and in most cases ovulations were characterized by normal progesterone concentrations in both groups. The effect of inositol on follicular maturation was rapid, because the circulating concentration of E2 increased only in the inositol group during the first week of treatment. Significant (P < 0.01) weight loss (and leptin reduction) was recorded in the inositol group, whereas in the placebo group was recorded an increase of the weight (P < 0.05). A significant increase in circulating high-density lipoprotein was observed only in the inositol-treated group. Metabolic risk factor benefits of inositol treatment were not observed in the morbidly obese subgroup of patients (body mass index > 37). No change in fasting glucose concentrations, fasting insulin, or insulin responses to glucose challenge test was recorded after 14-wk of inositol and placebo therapy. There was an inverse relationship between body mass of the patients and the efficacy of the treatment.

Conclusions: These data support a beneficial effect of inositol in improving ovarian function in women with oligomenorrhea and polycystic ovaries.