Menstruation delayed for 13 days, suddenly there was a small amount of bleeding, what's going on?

Patient's question:

No

Doctor's answer:

Menstrual disorders are regulated by the hypothalamic-pituitary-ovarian-gonadal axis. Various factors such as mental stress, emotional fluctuations, environmental changes, pregnancy, age, diseases, medications, and nutritional status can all cause dysfunction of this gonadal axis, leading to menstrual disorders.