PMS and PMDD are both linked to hormonal changes before menstruation, but PMDD is significantly more severe. Understanding the role of hormone fluctuations can help women seek appropriate diagnosis and treatment.

The menstrual cycle has four phases — menstrual, follicular, ovulation, and luteal — each regulated by key hormones. Cycle changes in timing, flow, or symptoms can be normal, but may also signal underlying hormonal or health issues.