Question

The principle behind the use of progesterone as a contraceptive is based on the naturally occuring events of a particular phase of the menstrual cycle. Which phase is it?

• A. Follicular phase
• B. Ovulatory phase
• C. Luteal phase
• D. Proliferative phase

Answer 1

The correct option is C Luteal phase

The principle behind the use of progesterone as a hormonal method of contraception lies in the fact that increased level of progesterone inhibits the secretion of GnRH from the hypothalamus. In the absence of GnRH, the anterior pituitary is not stimulated to release gonadotropins (LH and FSH). This is seen in the luteal phase of the menstrual cycle, where the increase in the level of progesterone has suppressed the further rise in levels of LH and FSH. Due to this, there is no development of follicles in the luteal phase.
During the follicular phase in a normal menstrual cycle, there is gradual increase in the levels of LH and FSH. This leads to the development of follicles under the influence of FSH. After a certain while, towards the terminal stage of the follicular phase, LH and FSH reach their respective peaks and ovulation occurs on the next day (ovulatory phase).
In the proliferative phase, the endometrial lining is rejuvenated under the influence of estrogen secreted by the developing follicles. There is development of uterine glands and blood vessels.
The synthetic progesterone in the hormonal contraceptives inhbits the events of follicular phase such as devlopment of follicles and secretion of estrogen from the ovary.