Which of the following hormones regulates the immune system ?

Options

A. Glucagon
B. Thyroxine
C. Thymosin
D. Adrenaline

Answer

To determine which hormone regulates the immune system, let's analyze the options provided:

1. **Glucagon**:
- **Function**: Glucagon is a hormone produced by the alpha cells of the islets of Langerhans in the pancreas. Its primary role is to increase blood glucose levels by converting glycogen into glucose.
- **Conclusion**: Glucagon does not regulate the immune system.

2. **Thyroxine**:
- **Function**: Thyroxine is a hormone secreted by the thyroid gland. It plays a crucial role in regulating metabolism and energy levels in the body.
- **Conclusion**: Thyroxine does not regulate the immune system.

3. **Adrenaline**:
- **Function**: Adrenaline, also known as epinephrine, is produced by the adrenal glands and is often referred to as the "fight or flight" hormone. It prepares the body for emergency situations by increasing heart rate and energy availability.
- **Conclusion**: Adrenaline does not regulate the immune system.

4. **Thymosin**:
- **Function**: Thymosin is a hormone secreted by the thymus gland. It is essential for the development and maturation of T-cells, which are critical components of the immune system. Thymosin also assists in the development of B-cells, which produce antibodies.
- **Conclusion**: Thymosin is involved in regulating the immune system.

Based on this analysis, the hormone that regulates the immune system is **Thymosin**.

### Summary:
The correct answer is **Thymosin**.