Biological Systems MCAT Practice Exam

What is the role of hCG during pregnancy?

1. It helps in the formation of the placenta.

2. It signals the beginning of menstruation.

3. It triggers the maturation of follicles.

4. It replaces LH to maintain the corpus luteum.

The correct answer is: It replaces LH to maintain the corpus luteum.

During pregnancy, human chorionic gonadotropin (hCG) plays a crucial role in maintaining the corpus luteum, which is essential for the early stages of pregnancy. After fertilization, the corpus luteum produces progesterone, which is vital for maintaining the uterine lining and supporting early embryonic development. hCG is secreted by the developing placenta shortly after implantation, and it effectively mimics the action of luteinizing hormone (LH). By doing so, it signals the corpus luteum to continue its hormone production, particularly progesterone, preventing its degeneration. This preservation of the corpus luteum is critical because it sustains the uterine environment favorable for fetal development until the placenta is fully formed and can take over hormone production later in the pregnancy. Other options do not accurately describe the primary function of hCG during pregnancy. For example, while hCG does play a role in early pregnancy management, it does not signal the beginning of menstruation nor does it directly assist in the maturation of follicles. Similarly, although the formation of the placenta is a significant part of pregnancy, hCG’s primary role is to support the corpus luteum. Thus, option D accurately conveys the importance of hCG in the early stages of pregnancy.