Hypomenorrhea depends on whether ovulation occurs first, and the definition of hypomenorrhea is that the menstrual flow is less than 5ml. What is the specific amount of 5ml? A daily sanitary towel is 5ml when it is almost soaked. Generally speaking, the more estrogen is secreted, the thicker the endometrium will be and the more menstrual flow will be. If the estrogen level is low, the endometrium will become thinner and the menstrual flow will be less. In addition, progesterone is produced after ovulation Progesterone can transform endometrium into secretory phase, and make endometrium relax and edema. When the level of progesterone drops, progesterone withdrawal bleeding occurs, which makes the endometrium completely fall off and form menstruation. The causes of menorrhagia include intrauterine adhesion, endometrial injury, polycystic ovary syndrome, endometrial tuberculosis, premature ovarian failure, hyperprolactinemia, oral contraceptives, abnormal thyroid function, excessive weight loss, mental and emotional factors, etc.