This document provides definitions and discusses the evaluation and treatment of amenorrhea and polycystic ovarian syndrome (PCOS). It defines types of amenorrhea and normal menstrual cycles. Evaluation includes pregnancy tests, hormone levels, and progestational challenges. Treatment depends on the underlying cause and may include birth control pills, progesterone, clomiphene, or metformin. PCOS is characterized by irregular periods and elevated androgens. Treatment focuses on weight loss, birth control pills, and improving insulin resistance.