MCAT Biology Question 30: Answer and Explanation
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Question: 30
15. Which of the following would NOT be seen during pregnancy?
- A. High levels of hCG in the first trimester
- B. High levels of progesterone throughout the pregnancy
- C. Low levels of FSH in the first trimester
- D. High levels of GnRH throughout the pregnancy
Correct Answer: D
Explanation:
During the first trimester of pregnancy, the corpus luteum is preserved by human chorionic gonadotropin (hCG); hence, progesterone secretion by the corpus luteum is maintained during the first trimester. This eliminates choice (A). During the second trimester, hCG levels decline, but progesterone levels rise because the hormone is now secreted by the placenta itself, eliminating choice (B). High levels of progesterone and estrogen inhibit GnRH secretion, thus preventing FSH and LH secretion and the onset of a new menstrual cycle. This eliminates choice (C) and validates choice (D).