Menstruation is caused by

Options

A. Increase in LH
B. Increase in estrogen
C. Increase in progesterone
D. Decrease in progesterone

Answer

**Step-by-Step Solution:**

1. **Understanding Menstruation**: Menstruation is a monthly process in the female reproductive system where the uterine lining is shed if there is no fertilization of an egg.

2. **Hormonal Regulation**: The menstrual cycle is regulated by hormones, primarily estrogen and progesterone, which are produced by the ovaries.

3. **Role of Progesterone**: Progesterone is crucial for maintaining the uterine lining after ovulation. If fertilization does not occur, the corpus luteum (which produces progesterone) regresses.

4. **Decrease in Progesterone**: When the corpus luteum regresses, the levels of progesterone decrease. This drop in progesterone is what triggers the shedding of the uterine lining.

5. **Conclusion**: Since menstruation occurs due to the shedding of the uterine lining caused by the decrease in progesterone, the correct answer to the question is option D: decrease in progesterone.

**Final Answer**: D. Decrease in progesterone.

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