Delayed menstruation in winter is supposed to be caused by delayed feedback due to hypothalamic dysfunction caused by external environmental factors. Women’s menstruation is controlled by the reproductive axis, which not only interacts with the hormone levels in the body, but is also affected by many external factors, such as temperature, environment, body weight, and emotions. In winter, when the temperature is low, the body’s basal metabolic rate slows down, and the demand for fat reserves rises, which can easily cause the hypothalamus to inhibit and produce lower levels of gonadotropins, which can cause prolonged follicle maturation, and then menstruation will be delayed. If a woman is underweight with low fat content, and consumes more fat in winter with less fat remaining, the body will exert its own regulatory mechanism to try to retain fat and blood volume so that feedback from the reproductive axis is delayed, which will cause delayed menstruation.