Myo-inositol is a vitamin-like compound that your body uses as part of its internal signalling system. It plays a key role in how cells respond to insulin and other hormones, which is why it has become an important focus in supporting conditions linked to insulin resistance, such as PCOS. Although small amounts are made in the body and found in foods like fruits, beans, and whole grains, higher intakes are often studied in supplement form when targeting hormone and cycle-related symptoms.