Most important component of oral contraceptive is
a. Thyroxine
b. LH
c. Progesterone
d. GH

Hint:
Currently, there are three varieties of pill pills: combined estrogen-progesterone, progesterone only and also the continuous or extended use pill. The foremost commonly prescribed pill is that the combined hormonal pill with estrogen and progesterone. Progesterone is that the hormone that stops pregnancy, and therefore the estrogen component will control menstrual bleeding. The pills which contain only progestin are called mini-pill.

Complete answer:
The Oral contraceptives/birth control pills are designed to be taken orally by women to stop pregnancy. It alters the cycle to eliminate ovulation and stop pregnancy. Oral contraceptives check ovulation by inhibiting secretion of FSH and LH which are necessary for ovulation. They're hormonal preparations which will contain combinations of the hormones estrogen and progestin or progestin alone which stops the ovaries from releasing eggs. The progesterone is primarily accountable for preventing pregnancy. The best mechanism of action is the prevention of ovulation; they inhibit follicular development and forestall ovulation. Progestogen feedback works at the hypothalamus to decrease the heartbeat frequency of gonadotropin releasing hormone. This, in turn, will decrease the secretion of follicle- stimulating hormone (FSH) and reduces the secretion of gonadotropic hormone (LH). If the follicle isn’t developing, then there's no increase within the estradiol levels (the follicle makes estradiol). The progestogen feedback and lack of estrogen feedback on LH secretion stop the mid-cycle LH surge. With no follicle developed and no LH surge to release the follicle, there's the prevention of ovulation. Estrogen has some effect with inhibiting follicular development thanks to its feedback on the ductless gland with slow FSH secretion; it’s just not as prominent because of the progesterone’s effect. Another primary mechanism of action is progesterone’s ability to inhibit sperm from penetrating through the cervix and upper genital tract by making the cervical mucus unfriendly.

Therefore, the correct answer is c, progesterone.

Note: Contraception pill is prescribed by many healthcare workers however, it's important to grasp about the potential side effects also. Regular monitoring of the patient is important to make sure that she isn't developing any serious side effects. It is also important to understand that oral contraceptives don't protect against sexually transmitted diseases and that the use of a condom is extremely recommended. Some medications can change the effectiveness of the pills if taken together and contrariwise.