FSH (Follicle Stimulating Hormone) is a hormone, released from the anterior pituitary gland. It is a gonadotropin, stimulating the ovary to produce hormones and ovulate.
FSH causes an ovarian follicle to develop and drives the pre-ovulatory rise in estrogen.
There is spike of FSH coincidental with the LH surge. These lead to ovulation within a few hours.
*These are general values taken from a variety of sources. The actual normal values may vary from lab to lab and from one type of testing protocol to another.