A major constituent of contraceptive pills is:

Explanation

The most commonly prescribed contraceptive pill is the combined hormonal pill with progesterone. Progesterone is primarily responsible for preventing pregnancy. The main mechanism of action is the prevention of ovulation; they inhibit follicular development and prevent ovulation. Progestogen-negative feedback works at the hypothalamus to decrease the pulse frequency of the gonadotropin-releasing hormone. This, in turn, will reduce the secretion of follicle-stimulating hormone (FSH) and decrease the secretion of luteinizing hormone (LH). If the follicle isn't developing, there is no increase in the estradiol levels (the follicle makes estradiol). The progestogen-negative feedback and lack of estrogen-positive feedback on LH secretion stop the mid-cycle LH surge. With no follicle developed and no LH surge to release the follicle, ovulation is prevented.