A graph plots hormone levels against the days of a 28-day menstrual cycle. Ovarian hormone X rises during the follicular phase and peaks just before day 14. Ovarian hormone Y stays low until ovulation, then rises to a peak around day 21 and falls by day 28 in the absence of fertilisation. Pituitary hormone Z shows a sharp peak at day 14. Which statement is correct?
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After ovulation, the remaining Graafian follicle becomes the corpus luteum, which secretes large amounts of progesterone essential for maintaining the endometrium. Without fertilisation the corpus luteum degenerates and menstruation follows.
- A.
The hormone secreted by growing follicles in the follicular phase is oestrogen.
- B.
It is the LH surge at mid-cycle that induces rupture of the Graafian follicle.
- D.
hCG rises only in pregnancy; Y falls because the corpus luteum degenerates.
NCERT: Class 12 Biology, Chapter 2, 2.4