The nature of FSH induction by GnRH.

Follicle-stimulating hormone (FSH), a major regulator of mammalian gonadal function, is induced by gonadotropin-releasing hormone (GnRH), but it is unclear how much induction is direct or indirect and what relevance each has in vivo. Two advances now make it possible to address these issues, which are central to understanding FSH regulation. The first is the use of transformed L beta T2 gonadotropes to define key promoter sequences of FSHB (the gene encoding the FSH-beta subunit) that are needed for induction by GnRH and/or other factors; and the second is the ability to express FSHB promoter-reporter constructs in transgenic mouse gonadotropes to test the physiological relevance of promoter elements identified by using L beta T2 cells. Here, we summarize past studies on GnRH induction of FSH, and propose questions and approaches for the future.