Thyroxine has an important role in regulating

Options

A. Blood calcium level
B. Basal metabolic rate
C. Water and electrolyte balance
D. Both (2) & (3)

Answer

### Step-by-Step Solution:

1. **Understanding Thyroxine**:
- Thyroxine is a hormone produced by the thyroid gland. It plays a crucial role in regulating various physiological processes in the body.

2. **Source of Thyroxine**:
- Thyroxine is secreted from the thyroid gland, which is stimulated by the thyroid-stimulating hormone (TSH) released from the anterior pituitary gland. The release of TSH is, in turn, regulated by the thyrotropin-releasing hormone (TRH) from the hypothalamus.

3. **Functions of Thyroxine**:
- Thyroxine is involved in several metabolic processes, including:
- Regulation of metabolism
- Control of energy expenditure
- Influence on growth and development
- Regulation of the basal metabolic rate (BMR)

4. **Regulating Basal Metabolic Rate (BMR)**:
- The basal metabolic rate is the rate at which the body expends energy at rest to maintain vital functions. Thyroxine increases the BMR by:
- Stimulating carbohydrate metabolism (glycogenesis and glycogenolysis)
- Enhancing fat metabolism and increasing fatty acid levels in the bloodstream
- Increasing blood cholesterol levels

5. **Conclusion**:
- Based on the functions of thyroxine, it is clear that its primary role is in regulating the basal metabolic rate. Therefore, the correct answer to the question is that thyroxine has an important role in regulating the **basal metabolic rate**.