What is the primary role of estrogen in the menstrual cycle?
To trigger ovulation
To maintain the corpus luteum
To stimulate endometrial proliferation
To inhibit FSH secretion
The Correct Answer is C
Estrogen function in the menstrual cycle
Estrogen is a key steroid hormone secreted primarily by the granulosa cells of the developing follicle. It plays a central role in the follicular phase of the menstrual cycle by stimulating endometrial proliferation, enhancing FSH receptor expression in follicles, and exerting negative feedback on FSH and positive feedback on LH as ovulation approaches. Normal estradiol (E2) levels range from 30–400 pg/mL, peaking around 200–300 pg/mL just before ovulation. Estrogen also supports cervical mucus thinning to facilitate sperm transport and primes the endometrium for possible implantation.
Rationale for correct answer
C. Estrogen stimulates mitotic activity and proliferation of the endometrial functional layer during the follicular phase. This prepares the uterine lining for potential implantation post-ovulation.
Rationale for incorrect answers
A. Ovulation is triggered by a surge in LH, not directly by estrogen. Estrogen contributes indirectly by reaching a threshold that induces the LH surge, but it does not trigger ovulation by itself.
B. Maintenance of the corpus luteum is supported by LH and, if pregnancy occurs, human chorionic gonadotropin (hCG). Estrogen does not sustain corpus luteum function.
D. Estrogen initially inhibits FSH secretion via negative feedback, but this is not its primary role. Its main function is endometrial proliferation and preparing the body for ovulation.
Take home points
- Estrogen stimulates the endometrial lining to proliferate during the follicular phase.
- LH, not estrogen, is the primary trigger for ovulation.
- Corpus luteum maintenance depends on LH or hCG, not estrogen.
- Estrogen has a dual feedback effect on FSH depending on its concentration and timing.
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Related Questions
Correct Answer is ["A","B","C","D"]
Explanation
Menstrual phase of the uterine cycle The menstrual phase marks the beginning of the uterine cycle and is initiated by a sudden drop in estrogen and progesterone levels due to corpus luteum regression in the absence of implantation. This hormonal decline leads to vasoconstriction of spiral arteries, ischemia, and shedding of the functional layer of the endometrium. Normal menstrual flow lasts 3–5 days, and blood loss averages 30–40 mL. Spiral artery spasms result in tissue necrosis, and rising estrogen levels only commence after menstruation is complete.
Rationale for correct answers
A. The withdrawal of estrogen and progesterone at the end of the luteal phase triggers endometrial breakdown and onset of menstrual bleeding.
B. The functional layer of the endometrium undergoes necrosis and is shed through the cervix and vagina as menstrual fluid.
C. Spiral arteries undergo intense vasoconstriction, leading to ischemia and necrosis of the endometrium, which causes menstruation.
D. The menstrual phase typically spans Days 1 to 5 of the cycle, marking the beginning of the uterine cycle before follicular estrogen rise.
Rationale for incorrect answers
E. Rising estrogen levels occur during the proliferative phase, which begins after menstruation. The menstrual phase is marked by low estrogen and progesterone levels.
Take home points
- Menstrual phase starts with progesterone and estrogen withdrawal.
- Endometrial shedding is due to spiral artery ischemia.
- Menstrual flow usually lasts 3–5 days.
- Rising estrogen levels define the proliferative phase, not the menstrual phase.
Correct Answer is C
Explanation
Estrogen function in the menstrual cycle
Estrogen is a key steroid hormone secreted primarily by the granulosa cells of the developing follicle. It plays a central role in the follicular phase of the menstrual cycle by stimulating endometrial proliferation, enhancing FSH receptor expression in follicles, and exerting negative feedback on FSH and positive feedback on LH as ovulation approaches. Normal estradiol (E2) levels range from 30–400 pg/mL, peaking around 200–300 pg/mL just before ovulation. Estrogen also supports cervical mucus thinning to facilitate sperm transport and primes the endometrium for possible implantation.
Rationale for correct answer
C. Estrogen stimulates mitotic activity and proliferation of the endometrial functional layer during the follicular phase. This prepares the uterine lining for potential implantation post-ovulation.
Rationale for incorrect answers
A. Ovulation is triggered by a surge in LH, not directly by estrogen. Estrogen contributes indirectly by reaching a threshold that induces the LH surge, but it does not trigger ovulation by itself.
B. Maintenance of the corpus luteum is supported by LH and, if pregnancy occurs, human chorionic gonadotropin (hCG). Estrogen does not sustain corpus luteum function.
D. Estrogen initially inhibits FSH secretion via negative feedback, but this is not its primary role. Its main function is endometrial proliferation and preparing the body for ovulation.
Take home points
- Estrogen stimulates the endometrial lining to proliferate during the follicular phase.
- LH, not estrogen, is the primary trigger for ovulation.
- Corpus luteum maintenance depends on LH or hCG, not estrogen.
- Estrogen has a dual feedback effect on FSH depending on its concentration and timing.
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