This book brings together the most up-to-date information about the physiology of progestogens. This volume addresses the bidirectional communication between hormones, fertility, tumors, and autoimmunity. It provides the basic science and clinical perspectives of progestogens which have not been previously available in one volume. In addition to estrogens, androgens, mineralocorticoids and glucocorticoids, progestogens are a major class of steroid hormone. While present in certain phases of estrous and menstrual cycles, progestogens are named for their function in maintaining pregnancy. This book is essentially practical in orientation, addressing the specific issues that confront the practitioner, and provides information to Obstetricians, Gynecologists, Reproductive endocrinologists, as well as Gynecological Oncologists and Rheumatologists. Contributions are from an international team of experts in the field.