Non iodinised hormone secreted by thyroid gland is :

Options

A. `T_(3)`
B. `T_(4)`
C. Calcitonin
D. Oxytocin

Answer

To solve the question regarding the non-iodinized hormone secreted by the thyroid gland, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Hormones Secreted by the Thyroid Gland**:
- The thyroid gland primarily secretes three hormones: T3 (triiodothyronine), T4 (thyroxine), and calcitonin.

2. **Understand the Composition of T3 and T4**:
- Both T3 and T4 are known as iodinated hormones because their synthesis requires iodine. T3 contains three iodine atoms, while T4 contains four.

3. **Identify the Non-Iodinized Hormone**:
- Calcitonin is the third hormone secreted by the thyroid gland. Unlike T3 and T4, calcitonin does not require iodine for its synthesis, making it a non-iodinized hormone.

4. **Eliminate Other Options**:
- Oxytocin is not secreted by the thyroid gland; it is produced by the pituitary gland. Therefore, it cannot be the answer.
- Since T3 and T4 are both iodinated hormones, they are not the correct answer.

5. **Conclusion**:
- The only non-iodinized hormone secreted by the thyroid gland is calcitonin.

### Final Answer:
The non-iodinized hormone secreted by the thyroid gland is **calcitonin**.

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