Apoptosis can occur by change in hormone levels in the ovarian cycle. When there is no fertilization of the ovum, the endometrial cells die because:
The involution of corpus luteum causes estradiol and progesterone levels to fall dramatically
LH levels rise after ovulation
Estradiol levels are not involved in the LH surge phenomenon
Estradiol inhibits the induction of the progesterone receptor in the endometrium