Estrogen produced during egg development exits the ovary, enters the bloodstream, and travels to the pituitary gland, where it exerts a negative feedback effect on the release of FSH and LH.

“So when estrogen is present at relatively low levels in females in the ovary, as it is during the development of these eggs, some of that estrogen, of course, is going to exit the ovary. It's going to go into the bloodstream. And it's going to travel back to the pituitary. Now, the pituitary can release things like follicle-stimulating hormone and luteinizing hormone. But the way I'd like you to think about the pituitary for sake of feedback loops is that it's sort of like a thermometer that you would put into a pool, like a backyard pool, that is attached to the heater.”