Menstruation is triggered by an abrupt decline in the amount of

Options

A. luteinising hormone
B. follicile-stimulating hormone
C. estrogen
D. progesterone

Answer

To answer the question "Menstruation is triggered by an abrupt decline in the amount of," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Menstrual Cycle**: The menstrual cycle is a monthly cycle that typically lasts about 28 days in human females. It involves various hormonal changes that prepare the body for potential pregnancy.

2. **Identifying Key Hormones**: There are four main hormones involved in the menstrual cycle:
- **Estrogen** (often referred to as "Astrosan" in the transcript)
- **Progesterone**
- **Follicle Stimulating Hormone (FSH)**
- **Luteinizing Hormone (LH)**

3. **Role of Progesterone**: Progesterone is produced by the corpus luteum after ovulation. Its primary role is to maintain the endometrium (the inner lining of the uterus) and prepare it for a potential implantation of a fertilized egg.

4. **Triggering Menstruation**: If fertilization does not occur, the corpus luteum degenerates, leading to a decrease in progesterone levels. This decline in progesterone is critical as it causes the endometrial lining to break down.

5. **Conclusion**: The abrupt decline in progesterone levels triggers menstruation, leading to the shedding of the endometrial lining.

### Final Answer:
Menstruation is triggered by an abrupt decline in the amount of **Progesterone** (Option 4).

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