Abstract: Primordial follicles are of the most abundant stage in the ovary, which serve as a source of all developing follicles. The pool of primordial follicles is essential for female fertility. Most primordial follicles remain quiescent, while few of them are initiated to grow, mature, and ovulate at last. The activation of primordial follicles is defined as a transition from primordial to primary follicle, which is regulated by multiple factors. The mechanisms underlying this activation are not completely stated. Recent studies showed that the growth differentiation factor 9 （GDF-9） and other factors promoted the activation of primordial follicles, while many factors, such as PTEN, inhibited the growth of primordial follicles to maintain the size of the primordial follicle pool. The regulation disorders may cause reproductive endocrine diseases. It is helpful for us to understand the physiology and pathology of human ovary and to provide theory of the fertility preservation, to explore the mechanisms regulating the activation of primordial follicles.

Key words: Ovarian follicle, Ovarian failure, premature, Transforming growth factor beta, Leukemia inhibitory factor, Anti-Mullerian hormone