In 1935, US-based physicians Irving Freiler Stein and Michael Leo Leventhal published “Amenorrhea Associated with Bilateral Polycystic Ovaries,” hereafter “Amenorrhea,” in the American Journal of Obstetrics and Gynecology based on their clinical experience with seven female patients. In their article, Stein and Leventhal report finding a correlation between a lack of menstruation for a prolonged period, or amenorrhea, in the women and the presence of bilateral polycystic ovaries, in which cysts form in both ovaries. Stein and Leventhal theorize that such cysts form due to hormonal imbalances, which makes their presence indicative of an endocrine, or hormonal, disorder. That explanation contested a widely held belief at the time that inflammation caused amenorrhea. “Amenorrhea” was one of the first publications to propose a hormonal explanation for bilateral polycystic ovaries and to describe the cluster of symptoms that became the basis for diagnosing what later became known as polycystic ovarian syndrome, or PCOS, an endocrine disorder that affects five to eleven percent of women globally per year.