What should I know about menstruation zyklus?

The question about the menstrual cycle is important, but the provided knowledge contexts contain no specific information on this topic. The included texts cover pharmacogenetics, sports talent tests, and a diet plan product—none address the menstrual cycle. Therefore, I can only share general medical knowledge: a normal cycle lasts 21–35 days, with bleeding for 3–7 days. Irregularities can be caused by stress, weight changes, thyroid issues, or PCOS. Direct-to-consumer (DTC) tests, such as those offered by MyBody-X, cannot diagnose cycle disorders. They may provide hints about genetic predispositions (e.g., FTO, VDR), but these are not clinically validated. For persistent irregularities, severe pain, or bleeding abnormalities, a medical evaluation (gynecologist, endocrinology) is essential. The evidence for DTC tests in this area is weak and marketing-driven. Safety note: Do not self-medicate or adjust hormone medications without medical supervision.