Parafollicular cells of thyroid secrete hormone for controlling level of

Options

A. (a) `K^(+)`
B. (b) `Na^(+)`
C. (c) `Ca^(2+)`
D. (d) `Mg^(2+)`

Answer

**Step-by-Step Solution:**

1. **Identify the Cells and Their Function**: The question refers to the parafollicular cells of the thyroid gland. These cells are known for their specific role in hormone secretion.

2. **Determine the Hormone Secreted**: Parafollicular cells secrete a hormone known as calcitonin. This is a polypeptide hormone.

3. **Understand the Role of Calcitonin**: Calcitonin plays a crucial role in regulating calcium levels in the blood. It primarily works to lower the concentration of calcium ions in the bloodstream.

4. **Mechanism of Action**: Calcitonin reduces blood calcium levels by:
- Increasing the absorption of calcium ions in the bones.
- Decreasing the reabsorption of calcium ions in the kidneys, leading to increased excretion of calcium.

5. **Evaluate the Options**: The question provides four options regarding which ion's level is controlled by the hormone secreted by parafollicular cells:
- A) Potassium ion
- B) Sodium ion
- C) Calcium ion
- D) Magnesium ion

6. **Select the Correct Answer**: Since calcitonin is specifically involved in regulating calcium levels, the correct answer is **C) Calcium ion**.

**Final Answer**: The parafollicular cells of the thyroid secrete a hormone for controlling the level of **calcium ion**.

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