This volume is devoted to all the aspects of prolactin. Medical management of prolactinomas can be based on our understanding of the physiology of hypothalamic control of the lactotroph. Armed with this knowledge, therapies for prolactinomas are highly successful and well tolerated. Because of the historical and practical importance of knowledge regarding the hypothalamus-lactotroph axis, the first chapters of this volume are dedicated to reviewing the physiology, development, and cell biology of lactotroph regulation. Chapters focusing on prolactinomas and related clinical issues follow these. Our understanding of the roles of PRL in the integration of maternal physiology is still very incomplete. The merger of genetics, developmental biology, and physiology has offered new avenues to study these essential functions. Several chapters in the text review our understandings of behavioural, reproductive, metabolic and developmental functions of PRL that relate to maternal care. The fundamental PRL signaling pathways, including relevant kinases, transcription factors, and comodulatory protein findings are reviewed from the receptor level to the nucleus. This volume gives a complete review on prolactin.