Which is true of thyrocalcitionin ?

Options

A. Produced by parathyroid, decreases Ca in ECF
B. Produced by thyroid, decreases Ca in ECF
C. Produced by parathyroid, increases Ca in ECF
D. Produced by thyroid, increase Ca in ECF.

Answer

**Step-by-Step Solution:**

1. **Understanding the Term "Thyrocalcitonin":**
- The term "thyrocalcitonin" can be broken down into two parts: "thyro" which refers to the thyroid gland, and "calcitonin" which is related to calcium regulation in the body.

2. **Source of Thyrocalcitonin:**
- Thyrocalcitonin, also known simply as calcitonin, is a hormone secreted by the thyroid gland.

3. **Nature of Thyrocalcitonin:**
- It is classified as a polypeptide hormone, which means it is made up of a chain of amino acids.

4. **Function of Thyrocalcitonin:**
- The primary function of thyrocalcitonin is to lower the concentration of calcium ions (Ca²⁺) in the blood and extracellular fluid (ECF). This is important for maintaining calcium homeostasis in the body.

5. **Role in Bone Formation:**
- By decreasing calcium levels in the blood, thyrocalcitonin promotes the deposition of calcium into the bones, thereby aiding in bone formation and strengthening.

6. **Conclusion:**
- Therefore, the correct statement regarding thyrocalcitonin is that it is produced by the thyroid gland and it decreases calcium levels in the blood and extracellular fluid.

**Final Answer:**
- The true statement about thyrocalcitonin is that it is produced by the thyroid gland and decreases calcium levels in the blood and extracellular fluid.

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