immature follicle

These "cysts" are actually immature follicles, not cysts ("polyfollicular ovary syndrome" would have been a more accurate name).

FSH is inhibited by inhibin (see below), at the same time LH and estrogen levels rise, which prevents immature follicles from continuing their growth.

Strips of cortical ovarian tissue can also be cryopreserved, but it must be re-implanted into the body to allow the encapsulated immature follicles to complete their maturation.