Hormonal influences, both natural and iatrogenic, are implicated in the most frequent health issues of women. Endometrial cancer is now the most common gynecologic cancer in the United States and the industrialized world. This cancer is strongly related to hormonal and metabolic factors. In addition, breast cancer treated with hormone therapy (Tamoxifen) may, in some cases, be associated with uterine pathology. Hormone therapy is used to improve the physiological effects and counteract abnormal and deleterious effects of “natural” hormonal activity. Millions of women receive hormone therapy at some point of their life: using oral contraceptives, reproductive technology, treatment for post-menopausal symptoms, among other uses. This book addresses a range of women’s health issues, from fertility to neoplasms, and their relationship with natural and iatrogenic hormonal effects. Chapters include clinical and pathological descriptions, theoretical and practical medical issues, and original studies and cases. Controversial issues in certain hormone therapies are presented with updated concepts based on clinical studies and novel statistical methods. The book will be useful for specialized and general physicians, oncologists, endocrinologists, researchers, medical students, and others in the field of women’s health.