Question

Which of the following statements about progesterone is false? a. Progesterone is secreted by the corpus luteum. b. Progesterone is secreted by the placenta. c. Progesterone decreases the basal body temperature. d. Progesterone secretion drops toward the end of the nonfertile luteal phase.

Short answer

The false statement about progesterone is: c. Progesterone decreases the basal body temperature. In fact, progesterone increases the basal body temperature.

Step-by-step solution

Review statement a.

Progesterone is secreted by the corpus luteum. This statement is true. After ovulation, the corpus luteum forms from the follicle and secretes progesterone to prepare the uterus for potential pregnancy.

Review statement b.

Progesterone is secreted by the placenta. This statement is also true. During pregnancy, the placenta takes over the role of producing progesterone to maintain the pregnancy and support fetal development.

Review statement c.

Progesterone decreases the basal body temperature. This statement is false. Progesterone actually increases the basal body temperature. When ovulation occurs and progesterone levels rise, there is a slight increase in basal body temperature, which can be used as an indication of ovulation.

Review statement d.

Progesterone secretion drops toward the end of the nonfertile luteal phase. This statement is true. If fertilization does not occur, the corpus luteum degenerates, and progesterone levels decrease, leading to menstruation. Given the analysis above, the correct answer is: c. Progesterone decreases the basal body temperature.

Key concepts

Corpus Luteum

The corpus luteum is an important structure in the female reproductive system. After ovulation, when the mature egg is released from the ovary, the remaining follicle transforms into the corpus luteum. This transformation is crucial because the corpus luteum becomes a temporary endocrine structure. It secretes hormones, mainly progesterone and some estrogen, to prepare the uterus for a potential pregnancy.
Progesterone from the corpus luteum plays a critical role in maintaining the endometrium, the lining of the uterus. This lining is where a fertilized egg would implant and grow. If no fertilization occurs, the corpus luteum degenerates after about two weeks, leading to a drop in progesterone and the onset of menstruation.

Placenta

The placenta is an organ that develops during pregnancy. It forms in the uterus and acts as a lifeline between the mother and the fetus. One of its critical functions is the production and secretion of progesterone. Initially, the corpus luteum produces progesterone to support early pregnancy.
As the pregnancy progresses, around the 8th to 12th week, the placenta takes over as the main source of progesterone. This transition is crucial because the hormone is essential for continuing to support the uterus, developing baby, and preventing contractions in the uterine wall that could lead to premature delivery.

• Provides nutrients and oxygen to the fetus
• Removes waste products
• Secretes hormones vital for pregnancy, including progesterone

The placenta's ability to produce progesterone ensures that pregnancy progresses smoothly and the fetus has a stable environment for development.

Basal Body Temperature

Basal body temperature (BBT) is the body's temperature at rest, typically measured first thing in the morning. Tracking BBT can be useful for understanding aspects of the menstrual cycle, especially ovulation. After ovulation, progesterone levels rise, leading to a slight increase in BBT.
The increase in temperature after ovulation is usually around 0.5 to 1 degree Fahrenheit. This change can be used by individuals trying to conceive or those trying to track their menstrual cycle more accurately. It's important to note that BBT must be measured consistently every morning before getting out of bed to ensure accuracy.
While BBT can provide valuable insights, it requires thorough and regular tracking for at least a few months to identify patterns in the menstrual cycle. The slight rise in temperature is associated with the body being in the luteal phase, or post-ovulation phase, of the menstrual cycle.

Menstrual Cycle

The menstrual cycle is a complex, repetitive cycle governing the female reproductive system. It prepares the body for potential pregnancy each month. The cycle is typically around 28 days, though it can vary from person to person. The cycle is divided into phases:

• Follicular Phase: Starts on the first day of menstruation and ends with ovulation. During this phase, the follicles in the ovary mature.
• Ovulation: The release of a mature egg from the ovary.
• Luteal Phase: After ovulation, the corpus luteum forms and secretes progesterone to prepare the uterus for a potential pregnancy.
• Menstruation: If no fertilization occurs, the corpus luteum degenerates, leading to a decrease in progesterone, and the uterine lining is shed.

Hormonal regulation, primarily by estrogen and progesterone, orchestrates each phase of the cycle. Understanding the menstrual cycle can provide insights into reproductive health and detect possible issues early.