<p>Menstrual cycle disorders include all deviations from a regular menstrual bleeding pattern. They are systematically classified by the simplified World Health Organization (WHO) classification or the hypothalamus, pituitary, ovary—polycystic ovary syndrome (HyPO-P) scheme of the Fédération Internationale de Gynécologie et d’Obstétrique (FIGO). Depending on the extent of the ovulatory dysfunction, the spectrum ranges from intermenstrual bleeding to amenorrhea as the maximum variant. A diagnostic work-up is obligatory to identify underlying causes. In addition to the clinical history and examination this is based on the hormonal analysis of ovarian regulation and any disruptive factors. If possible, causal treatment should be initiated. Otherwise, apart from ovarian stimulation for patients who wish to conceive and depending on the personal situation and other symptoms of the patient, the focus is on cycle regulation, endometrial transformation or avoiding other risks such as estrogen deficiency.</p>