The action of which of the following hormone is blocked during the use of RU 486 (mifepristone) ?

Options

A. FSH
B. LH
C. Progesterone
D. hCG

Answer

**Step-by-Step Solution:**

1. **Understanding RU-486 (Mifepristone):** RU-486, also known as mifepristone, is a medication used to induce abortion. It is classified as an anti-pregnancy drug.

2. **Mechanism of Action:** Mifepristone works by blocking the action of certain hormones in the body. Specifically, it binds to the receptors of progesterone, a hormone crucial for maintaining pregnancy.

3. **Role of Progesterone:** Progesterone is produced primarily by the ovaries and is essential for preparing the endometrium (the lining of the uterus) for implantation of a fertilized egg. It helps maintain the thickness of the endometrium throughout the pregnancy.

4. **Effect of Mifepristone on Progesterone:** When mifepristone is administered, it competes with progesterone for binding to its receptors in the uterus. As a result, progesterone cannot bind to its receptors, which leads to the breakdown of the endometrial lining and ultimately causes abortion.

5. **Conclusion:** Therefore, the hormone whose action is blocked by RU-486 (mifepristone) is progesterone.

**Final Answer:** The action of progesterone is blocked during the use of RU-486 (mifepristone).

---