Figure 2.

Alternative models for the creation and maintenance of the ovarian reserve. During the pre-pubertal period, primordial follicles are lost at a high rate that is slowed at the time of the FSH surge. Models where the number of initial follicles is increased show an increased rate of loss so that they reach typical numbers of follicles, indicating a quorum-sensing model with a ‘set point’ for follicle number. Stem cell supplementation models propose that the number of follicles can be increased throughout reproductive life. The Tilly stem cell model indicates a constant number of oocytes is created from stem cells. We favor a model in which the initial follicle pool is established at birth and these follicles are necessary to adult fertility (there are no additional follicles added to the pool) and sufficient to the fertility needs of the adult (follicle loss is not so much to prematurely lose all follicles.).