Myo-inositol (MYO) and D-chiro-inositol (DCI) are naturally occurring sugar-like compounds (inositols) crucial for cell signaling, especially in insulin and hormone regulation, commonly combined in supplements for Polycystic Ovary Syndrome (PCOS) to improve insulin sensitivity, restore ovulation, and support fertility. MYO helps glucose uptake, while DCI aids in glycogen storage, and together, especially in a natural 40:1 ratio, they balance hormones like LH/FSH, reduce androgens, and enhance egg quality, with potential benefits for metabolic health and mood disorders.