The combined effect of estrogen and progesterone to prevent pregnancy are
The pill encourages the degeneration of corpus Luteum
The pill prevents follicular development by inhibiting the release of GnRH, FSH and LH.
The causes of the above mentioned effects are described below:
1. The combined effect of the 2 hormones in the contraceptive pill suppresses the FSH (follicle stimulating hormone) and LH (luteinizing hormone) by decreasing the release of FSH-RH (follicle stimulating hormone releasing factors) because of inhibition of hypothalamus due to the estrogen hormone. Due to the suppression of FSH and LH ovulation do not occur as FSH helps to mature follicles and LH surge causes ovulation.
2. Estrogen also causes degeneration of corpus luteum that causes fall of progesterone level and leads to onset of bleeding by shedding of the endometrial lining so to maintain the thickening of the endometrial lining progesterone is combined with estrogen in the pill. 3.
3. Progesterone maintains the thickening of the endometrial layer of the uterus so that it can hamper the passageway to transport the sperm to fertilize the egg and also progesterone inhibits the ovulation.