Myo-inositol (myo-Ins) and D-chiro-inositol (D-chiro-Ins) are natural compounds involved in many biological pathways. Since the discovery of their involvement in endocrine signal transduction, myo-Ins and D-chiro-Ins supplementation has contributed to clinical approaches in ameliorating many gynecological and endocrinological diseases. Currently both myo-Ins and D-chiro-Ins are well-tolerated, effective alternative candidates to the classical insulin sensitizers, and are useful treatments in preventing and treating metabolic and reproductive disorders such as polycystic ovary syndrome (PCOS), gestational diabetes mellitus (GDM), and male fertility disturbances, like sperm abnormalities. Moreover, besides metabolic activity, myo-Ins and D-chiro-Ins deeply influence steroidogenesis, regulating the pools of androgens and estrogens, likely in opposite ways. Given the complexity of inositol-related mechanisms of action, many of their beneficial effects are still under scrutiny. Therefore, continuing research aims to discover new emerging roles and mechanisms that can allow clinicians to tailor inositol therapy and to use it in other medical areas, hitherto unexplored. The present paper outlines the established evidence on inositols and updates on recent research, namely concerning D-chiro-Ins involvement into steroidogenesis. In particular, D-chiro-Ins mediates insulin-induced testosterone biosynthesis from ovarian thecal cells and directly affects synthesis of estrogens by modulating the expression of the aromatase enzyme. Ovaries, as well as other organs and tissues, are characterized by a specific ratio of myo-Ins to D-chiro-Ins, which ensures their healthy state and proper functionality. Altered inositol ratios may account for pathological conditions, causing an imbalance in sex hormones. Such situations usually occur in association with medical conditions, such as PCOS, or as a consequence of some pharmacological treatments. Based on the physiological role of inositols and the pathological implications of altered myo-Ins to D-chiro-Ins ratios, inositol therapy may be designed with two different aims: (1) restoring the inositol physiological ratio; (2) altering the ratio in a controlled way to achieve specific effects.

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In this study, kisspeptin had a positive correlation with LH and leptin levels in PCOS. In fact, the serum levels of kisspeptin and leptin does not differ statistically between PCOS and healthy women. There are limited data in the literature with regard to changes in kisspeptin levels and its relation with metabolic and hormonal disturbances.

Recently, myoinositol (myo-ins) and folic acid combination has gained an important role for treating Polycystic Ovary Syndrome (PCOS), in addition to combined oral contraceptives (COC). We aimed to examine myo-ins effects on anti-Mullerian hormone (AMH) levels and compare them with those ones obtained administering COC. In this prospective study, 137 PCOS patients, diagnosed according to Rotterdam criteria and admitted to the Reproductive Endocrinology and Infertility Outpatient Clinic at Dokuz Eylul University (Izmir, Turkey), were included. After randomization to COC (n = 60) and myo-ins (n = 77) arms, anthropometric measurements, blood pressure, Modified Ferriman Gallwey scores were calculated. Biochemical and hormonal analysis were performed, and LH/FSH and Apo B/A1 ratios were calculated. Data analysis was carried out in demographically and clinically matched 106 patients (COC = 54; myo-ins = 52). After 3-month treatment, increase in HDL and decreases in LH and LH/FSH ratio were statistically more significant only in COC group when compared with baseline (in both cases p > 0.05). In myo-ins group, fasting glucose, LDL, DHEAS, total cholesterol, and prolactin levels decreased significantly (for all p < 0.05). Progesterone and AMH levels, ovarian volume, ovarian antral follicle, and total antral follicle counts lessened significantly in both groups (for all p < 0.05). In PCOS treatment, MYO is observed more effective in reductions of total ovarian volume and AMH levels.