Question

On day 21 of a 28-day menstrual cycle, which hormone profile is correct?

• A. $\uparrow P, \uparrow E, \downarrow FSH, \downarrow LH$
• B. $\uparrow P, \downarrow E, \downarrow FSH, \downarrow LH$
• C. $\downarrow P, \downarrow E, \uparrow LH, \uparrow FSH$
• D. $\uparrow E, \downarrow P, \uparrow LH, \downarrow FSH$

Hint:

Day 21 = luteal phase = high progesterone with suppressed FSH and LH.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Day 21 of a standard 28-day cycle corresponds to the mid-luteal phase. This is the period after ovulation has occurred and the corpus luteum is fully active.
Step 2: Detailed Explanation:

Progesterone ($\uparrow$P): The corpus luteum secretes high levels of progesterone, which peak around day 21. This hormone is essential for secretory transformation of the endometrium to support implantation.

Estrogen ($\downarrow$E): While there is a secondary luteal peak of estrogen, it is significantly lower than the massive pre-ovulatory peak seen on Day 12-13. Relative to the ovulatory peak, estrogen is considered to be on the decline or lower in the luteal phase compared to the peak.

Gonadotropins ($\downarrow$FSH, $\downarrow$LH): High levels of progesterone and estrogen exert strong negative feedback on the hypothalamus and anterior pituitary.
This feedback inhibits the secretion of GnRH, FSH, and LH, ensuring that no new follicles begin to mature during the potential early pregnancy phase.

Clinical Use: Measuring serum progesterone on Day 21 is a standard test to confirm that ovulation has successfully taken place in that cycle.

Step 3: Final Answer:
The mid-luteal phase is characterized by high Progesterone and suppressed levels of FSH and LH due to negative feedback.