Question

The following graph shows the levels of pituitary hormones during a menstrual cycle. What do 1 and 2 represent ?

a. 1-LH, 2-FSH
b. 1-Estrogen, 2- progesterone
c. 1-FSH, 2- LH
d. 1- Progesterone, 2- Estrogen

Answer 1

GnRH is secreted by the hypothalamus which stimulates the anterior lobe of the pituitary gland to secrete LH and FSH. FSH stimulates the growth of graafian follicles and also helps in development of oocytes within the graafian follicle. It also helps to stimulate the estrogen hormone. LH stimulates the corpus luteum to secrete progesterone. When the level of progesterone increases it inhibits the release of GnRH. Hence, it stops the secretion of FSH.

Complete answer:
Option a is correct because during ovulation the level of FSH and LH increases. Here, FSH helps in proliferation of graafian follicles whereas, LH helps in secretion of progesterone from corpus luteum.

Option b is not correct as the level of progesterone is low because LH hormone is responsible to help in secretion of progesterone. So, its level increases after ovulation. If pregnancy is achieved then the progesterone level will be maintained by the corpus luteum by continuous secretion and if not then the corpus luteum degenerates and the level of progesterone becomes low

Option c is not correct because the level of the LH becomes high on the 14th day as compared to FSH.

Option d is not correct because the level of progesterone is low on the 14th day and it's amount increases gradually after the rupture of the graafian follicle or called ovulation.

Note:
1. The menstrual cycle in woman is about 28 to 30 days and you can also calculate when will ovulation occur by formula:
Ovulation= Menstrual cycle (average for about months) - 14 days
2. During the ovulatory phase the level of LH is so high it is called as LH surge, it helps the graafian follicle to rupture and release the hormone called progesterone.