Why do some women fail to menstruate regularly?

Some women may fail to menstruate regularly due to a variety of factors, including hormonal imbalances, stress, significant weight changes, or underlying health conditions such as polycystic ovary syndrome (PCOS) or thyroid disorders. Lifestyle factors like excessive exercise or poor nutrition can also disrupt the menstrual cycle. Additionally, certain medications or contraceptives may impact menstrual regularity. Understanding the underlying causes is crucial for addressing the issue effectively.