Anti-Mullerian hormone attenuates the effects of FSH on follicle development in the mouse ovary

Although ovarian follicle growth is under the influence of many growth fact ors and hormones of which FSH remains one of the most prominent regulators. Therefore, factors affecting the sensitivity of ovarian follicles to FSH a re also important for follicle growth. The aim of the present study was to investigate whether anti-Mullerian hormone (AMH) has an inhibitory effect o n follicle growth by decreasing the sensitivity of ovarian follicles to FSH . Furthermore, the combined action of AMH and FSH on ovarian follicle devel opment was examined. Three different experiments were performed. Using an i n vitro follicle culture system it was shown that FSH-stimulated preantral follicle growth is attenuated in the presence of AMH. This observation was confirmed by an in vivo experiment showing that in immature AMH-deficient f emales, more follicles start to grow under the influence of exogenous FSH t han in their wild-type littermates. In a third experiment, examination of t he follicle population of 4-mouth-old wildtype, FSH beta-, AMH-, and AMH-/F SH beta -deficient females revealed that loss of FSH expression has no impa ct on the number of primordial and preantral follicles, but the loss of inh ibitory action of AMH on the recruitment of primordial follicles in AMH-def icient mice is increased in the absence of FSH. In conclusion, these studie s show that AMH inhibits FSH-stimulated follicle growth in the mouse, sugge sting that AMH is one of the factors determining the sensitivity of ovarian follicles for FSH and that AMH is a dominant regulator of early follicle g rowth.