12-year-old why menstruation does not come

12-year-old why menstruation does not come once, the reasons are ovarian function development is not perfect, ovarian function development is not perfect, polycystic ovary syndrome, etc. 1. Ovarian function development is not perfect 12-year-old girls are in the early stages of puberty, ovarian function is not fully mature. This means that hormone levels in the body may be unstable, resulting in irregular menstrual cycles. Therefore, after menstruation does not come may be a normal phenomenon in the process of ovarian function development, do not worry too much. With the growth of age and ovarian function gradually perfect, menstrual cycle will gradually tend to regular.2. Adolescent physiological fluctuations Adolescent girls hormone levels fluctuate greatly, this fluctuation not only affects the menstrual cycle, but also may affect other aspects of the body. Therefore, post-menarche irregularities are part of the physiological fluctuations of puberty, and the menstrual cycle will gradually stabilize as the body gradually adapts and development.3. Polycystic ovary syndrome Polycystic ovary syndrome is a common endocrine disease, mainly characterized by high androgen levels and menstrual abnormalities. If a 12-year-old girl has polycystic ovary syndrome, it may also lead to irregular menstruation or even amenorrhea.