Regarding the hormonal changes during the menstrual cycle, all of the following statements are correct EXCEPT:

Explanation

## Hormonal Dynamics of the Menstrual Cycle ### Follicular Phase Estradiol Pattern **Key Point:** Estradiol does NOT remain consistently elevated throughout the follicular phase. Instead, it follows a biphasic pattern: - **Early follicular phase (days 1–5):** Estradiol is low (baseline ~30–50 pg/mL) as the corpus luteum regresses - **Mid-to-late follicular phase (days 5–14):** Estradiol rises progressively as the dominant follicle develops - **Peak:** Estradiol reaches its maximum (~200–400 pg/mL) 24–36 hours *before* ovulation - **Post-ovulation (early luteal):** Estradiol dips briefly before rising again during mid-luteal phase ### Why the Other Options Are Correct | Hormone | Timing | Mechanism | |---------|--------|----------| | FSH | Rises in late luteal phase (days 25–28) | Falling progesterone and inhibin from regressing corpus luteum remove negative feedback | | LH surge | 24–36 hrs before ovulation | Triggered by sustained high estradiol (positive feedback on anterior pituitary) | | Progesterone | Peaks mid-luteal (day 21 ± 2) | Corpus luteum secretes maximal progesterone 7–8 days post-ovulation | **High-Yield:** The estradiol profile is NOT a plateau but a **rise-peak-dip-rise** pattern. This biphasic estradiol secretion (follicular phase peak + luteal phase secondary rise) is critical for cycle regulation. **Clinical Pearl:** Abnormally sustained high estradiol in the follicular phase (e.g., in PCOS or estrogen-secreting tumors) can cause anovulation or irregular cycles by disrupting the normal LH surge timing.