What is the main hormonal change associated with the luteal phase of the menstrual cycle?

• A. Increased estrogen levels
• B. Increased progesterone levels
• C. Decreased follicle-stimulating hormone (FSH)
• D. Decreased luteinizing hormone (LH)

Answer: (B)

During the luteal phase of the menstrual cycle, the primary hormonal change is an increase in progesterone levels. After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes progesterone. This hormone plays a crucial role in preparing the endometrium for a potential implantation of a fertilized egg. It also helps maintain the uterine lining during the early stages of pregnancy if fertilization occurs.

In the context of the menstrual cycle, progesterone works in conjunction with estrogen, but its levels are notably higher during the luteal phase compared to the follicular phase. This increase in progesterone serves to create a supportive environment for a potential pregnancy, inhibiting further ovulation and promoting changes in the uterine lining.

While estrogen is also present and plays important roles during the luteal phase, the hallmark change that defines this phase is the rise in progesterone due to the activity of the corpus luteum. This elevation in progesterone is essential for a successful implantation and maintenance of early pregnancy. Other hormonal changes, such as decreased levels of FSH and LH, occur but are secondary to the primary increase in progesterone.