12-year-old girl menstruation came 2 times and did not come again, at this time the girl is in puberty, may be physiological reasons, but does not rule out pathological factors, such as weight loss, mood swings, secondary amenorrhea and so on. 1. Physiological factors. (1) adolescent girls, the hypothalamus – pituitary – ovarian axis of the feedback regulation between hormones is immature, most of the menstrual period is not too regular, such as no other discomfort can be observed. (2) By internal and external factors, such as physical fitness, excessive emotional fluctuations and environmental changes, leading to disorders in the regulation of ovarian hormones, irregular menstruation can also occur. 2. Pathological factors: For example, in secondary amenorrhea, dysfunction of the hypothalamus and ovaries may cause changes in hormone levels in the body, leading to hormonal abnormalities and menopause. If a 12-year-old girl has abnormal menstruation, it is recommended to go to the hospital in time, follow the doctor’s instructions for further examination, with the help of the doctor to clarify the cause, and targeted treatment or treatment.