Which one of the following is not a placental hormone?

Options

A. HCG
B. HCS
C. Progesterone
D. Melatonin

Answer

To determine which of the following is not a placental hormone, we need to first understand what placental hormones are and which hormones are produced by the placenta during pregnancy.

### Step-by-Step Solution:

1. **Understand the Role of the Placenta**: The placenta is an organ that develops during pregnancy, serving as a connection between the mother and the developing embryo. It facilitates the exchange of nutrients, gases, and waste products.

2. **Identify Hormones Produced by the Placenta**: The placenta acts as an endocrine organ and produces several hormones that are crucial for maintaining pregnancy. Key hormones include:
- **Human Chorionic Gonadotropin (HCG)**: This hormone is produced shortly after implantation and is responsible for maintaining the corpus luteum, which in turn produces progesterone during the early stages of pregnancy.
- **Human Placental Lactogen (HPL)**: This hormone helps prepare the mammary glands for lactation and plays a role in regulating maternal metabolism.
- **Estrogen and Progesterone**: These hormones are essential for maintaining pregnancy and preparing the body for childbirth.

3. **Identify the Non-Placental Hormone**: Among the hormones mentioned, we need to identify which one is not produced by the placenta.
- **Melatonin**: This hormone is produced by the pineal gland and is primarily involved in regulating sleep-wake cycles and pigmentation. It is not produced by the placenta.

4. **Conclusion**: Based on the information gathered, the hormone that is not a placental hormone is **Melatonin**.

### Final Answer:
**Melatonin** is not a placental hormone.

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