Which statement is not true about thyroxine?

Options

A. Iron is essential for the synthesis of thyroxine
B. It regulates carbohydrates, protein and fat metabolism in the body
C. Thyroid gland requires iodine to synthesise thyroxine
D. Thyroxine is also called thyroid hormone

Explanation

To determine which statement is not true about thyroxine, we will analyze each statement provided regarding this hormone.

### Step-by-Step Solution:

1. **Identify the Hormone**: Thyroxine is a hormone secreted by the thyroid gland. It plays a crucial role in regulating metabolism in the body.

2. **Evaluate the Statements**:
- **Statement 1**: "Iron is essential for the synthesis of thyroxine."
- This statement is **not true**. The synthesis of thyroxine requires **iodine**, not iron.

- **Statement 2**: "Thyroxine regulates carbohydrates, proteins, and fat metabolism in the body."
- This statement is **true**. Thyroxine is involved in the regulation of overall metabolism, including carbohydrates, proteins, and fats.

- **Statement 3**: "Thyroid gland requires iodine to synthesize thyroxine."
- This statement is **true**. Iodine is indeed necessary for the synthesis of thyroxine.

- **Statement 4**: "Thyroxine is also called thyroid hormone as it is secreted by the thyroid gland."
- This statement is **true**. Thyroxine is commonly referred to as the thyroid hormone because it is produced by the thyroid gland.

3. **Conclusion**: After evaluating all the statements, the statement that is not true about thyroxine is **Statement 1**: "Iron is essential for the synthesis of thyroxine."

### Final Answer:
The statement that is not true about thyroxine is: **"Iron is essential for the synthesis of thyroxine."**

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