Which of the following is used in the treatment of thyroid cancer?

Options

A. `I_131`
B. `U_238`
C. `Ra_224`
D. `C_14`

Answer

**Step-by-Step Solution:**

1. **Understanding Thyroid Cancer**: The thyroid gland is the largest endocrine gland in the body, responsible for producing hormones like thyroxine (T4) and triiodothyronine (T3). Thyroid cancer occurs when there is an uncontrolled growth of cells in the thyroid gland.

2. **Role of Iodine in Thyroid Function**: The production of thyroid hormones requires iodine. Iodine is an essential mineral that is incorporated into the structure of T3 and T4 hormones.

3. **Treatment Options for Thyroid Cancer**: In the treatment of thyroid cancer, radioactive iodine is commonly used. This is because the thyroid gland absorbs iodine, and using a radioactive form allows for targeted treatment of cancerous cells.

4. **Identifying the Correct Radioactive Iodine**: Among the various radioactive isotopes, Iodine-131 is specifically used for the diagnosis and treatment of thyroid cancer. It is effective because it can be taken up by the thyroid cells, allowing for both imaging and therapeutic effects.

5. **Excluding Other Options**: Other radioactive elements such as Carbon-14, Radium-224, and Uranium-238 do not have a role in the treatment of thyroid cancer. They are not absorbed by the thyroid gland and therefore are not effective for this purpose.

6. **Conclusion**: Based on the information above, the correct answer to the question of which substance is used in the treatment of thyroid cancer is Iodine-131.

**Final Answer**: Iodine-131

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