Gonadotropins in the Female
Biosynthetic steps in steroidogenesis and the presence of cell-surface receptors for gonadotropins are depicted in both cell types of the ovarian follicle. Dashed lines associated with gonadotropins and their receptors denote binding and/or facilitation of steroid biosynthesis. Rabbits are unique because progesterone secretion is indirectly sustained by the action of estrogen produced by ovarian follicles in response to the action of gonadotropins. Circulating concentrations of both gonadotropins are usually somewhat elevated during the first few weeks, months, or years of life. As the females approach puberty, ovarian secretions do appear to suppress gonadotropins, but there is a selective hypersecretion of gonadotropins during the period of sleep in human females as they initiate puberty just as occurs in peripubertal human males. As occurs in the male, photoperiod exerts a major influence on female reproduction in some species.