(Mostly because, in a natural cycle, estrogen
is released after FSH and LH have triggered the follicles to start growing. <span style = 'background-color: #dae8f4'>estrogen</span>
is what turns off FSH production. Then the rising <span style = 'background-color: #dae8f4'>estrogen</span>
triggers a surge of LH, which of course triggers the egg to be released. But, when you gave high enough doses of estrogen
right from the start, it starts telling your body to stop FSH production before it ever begins, see?