Women spend approximately 9 years of their lives in poor health, which is 25 percent more than men. Unlike men, these years of poor health in women are not concentrated at the end of life, but rather extend from the period of first menstruation to menopause. In the past decade, researchers have discovered significant gender differences in how diseases manifest, how they progress, and how they respond to treatment, including for conditions that affect both sexes, such as cardiovascular disease. In addition to diseases common to both sexes, there are disorders that occur exclusively in women and girls. Although benign, these female-specific disorders pose a significant burden and affect the female reproductive organs or the hormonal systems that regulate them. Investing in women's health is therefore a social necessity.