Staying up late can affect the menstrual cycle because when you stay up late, your mind is in a high state of tension and your hormone levels change due to fatigue, which can lead to early or even delayed menstruation. Also, staying up late can affect the metabolism of the body and may induce abnormalities in thyroid function, which can cause changes in the menstrual cycle when thyroid disease is present. Staying up late at night can cause prolactinemia and polycystic ovaries due to prolonged mental stimulation, which can also affect the menstrual cycle. In normal times, you must develop good habits, do not overwork and do not stay up too late to avoid hormonal disorders, which require medication and may take a longer time.