According to the text, during the follicular phase leading up to ovulation, the growing follicles secrete estrogens (oestradiol), and both LH and FSH attain a peak level. The rapid secretion of LH (LH surge) induces the rupture of the fully developed Graafian follicle and the release of the ovum (secondary oocyte). Therefore, ovulation is associated with peak levels of oestrogen and LH, and the rupture of the mature follicle, not a decrease in oestradiol.