Estrogen is the primary sex hormone in women and it functions during the reproductive menstrual cycle. Women have three major types of estrogen: estrone, estradiol, and estriol, which bind to and activate receptors within the body. Researchers discovered the three types of estrogen over a period of seven years, contributing to more detailed descriptions of the menstrual cycle. Each type of estrogen molecule contains a slightly different arrangement or number of atoms that in turn causes some of the estrogens to be more active than others. The different types of estrogen peak and wane throughout women's reproductive cycles, from normal menstruation to pregnancy to the cessation of menstruation (menopause). As scientists better explained the effects of estrogens, they used that information to develop oral contraceptives to control pregnancy, to map the menstrual cycle, and to create hormone therapies to regulate abnormal levels of estrogen.

The figure depicts three different molecular structures of estrogen found in mammals’ that differ by the arrangement of bonds and side groups. The molecular structures of the three estrogen molecules differ by the arrangement of chemical bonds and side groups attached to the core steroid structure, cholesterol, which contains three cyclohexane rings and one cyclopentane ring.

Christine Jorgensen was a transgender woman and activist in the United States who lived during the twentieth century. She was one of the first US citizens to publicly disclose her gender transition from male to female through gender-affirming surgery and hormone replacement therapy. By 1949, when Jorgensen began her transition, few individuals had undergone gender transition. Various popular media outlets reported on Jorgensen’s gender transition and surgery, which allowed Jorgensen to educate the American public on topics such as gender identity and sexual orientation. Jorgensen authored an autobiography in 1967, which detailed the journey of her life from early childhood to the end of her forties. Although many transgender people continue to fight for acceptance and equality in the US as of 2024, Jorgensen’s advocacy and activism increased transgender awareness for the general public at a time when existing and living openly as a transgender person received little recognition and support.

Menopause is defined as the point in time exactly twelve months after a female has had her last menstrual period, or shedding of the lining of the uterus. As a female ages, the hormone levels that drive menstruation decrease, beginning the process of perimenopause, which eventually leads to menopause and can result in various symptoms including depression, difficulty sleeping, and hot flashes, or abrupt feelings of heat typically in the upper body. Once a female reaches menopause, those symptoms typically subside, but after menopause, the risk of other health conditions such as osteoporosis, or brittle bones, increases. At least since the fourth century BCE, researchers understood that menopause occurred in females but held many negative ideas and misconceptions about the process, which resulted in stigma that left females uninformed about what happened to their bodies as they aged. Research on and perceptions towards menopause evolved over the twentieth century, and as of 2024, researchers understand it as a typical part of aging and development in females, marking the end of their reproductive years.