Question

When an egg is fertilized and pregnancy occurs, which of the following is correct regarding hormone concentrations?

A) Progesterone levels drop, whereas estrogen levels remain high.
B) Both progesterone and estrogen levels drop.
C) Both progesterone and estrogen levels rise.
D) Progesterone levels remain high, whereas estrogen levels drop.

Answer 1

Hint Fertilisation is the process of fusion of sperm and ovum. The ovulation (ovulatory phase) is followed by the luteal phase during which the remaining parts of the graffian follicle transform as corpus leuteum and it secretes a large amount of progesterone which is essential for the maintenance of endometrium.
Complete Step-by-step answer:
Corpus leuteum produces progesterone that is important for endometrium and such endometrium is necessary for implantation of the fertilized ovum and other events of pregnancy.
During pregnancy, all events of the menstrual cycle and there is no menstruation. In case of no fertilization, the corpus luteum degenerates. Degeneration of corpus luteum leads to the disintegration of endometrium leading to menstruation, marking a new cycle.
During the follicular phase, the primary follicles in the ovary grow to become fully mature graffian follicles and at the same time, the endometrium of the uterus regenerates through proliferation. These changes in the ovary and the uterus are induced by the changes in the levels of pituitary and ovarian hormones.
Estrogen levels increase before ovulation in the follicular or proliferative phase.
Hence the correct answer is option D.
Note: In human beings, the menstrual cycle ceases around 50 years of age; That is called menopause. Cyclic menstruation is an indicator of the normal reproductive phase and extends between menarche and menopause.