What role does pituitary gonadotropins play during follicular and ovulatory phases of menstrual cycle ? Explain the shifts in steroidal secretions.

The secretion of gonadotropins ($LH$ and $FSH$) increases gradually during the follicular phase and stimulates follicular development as well as secretion of estrogens by the growing follicles.

In the middle of cycle (about $14^{\text {th }}$ day) both $LH$ and $FSH$ attain a peak level.