Which two hormones are responsible for the regulation of calcium and phosphorus in the blood?

Answer

**Step-by-Step Solution:**

1. **Identify the Hormones**: The two hormones responsible for the regulation of calcium and phosphorus in the blood are Calcitonin and Parathyroid Hormone (PTH).

2. **Source of Hormones**:
- Calcitonin is produced by the Thyroid Gland.
- Parathyroid Hormone is produced by the Parathyroid Glands.

3. **Function of Calcitonin**:
- Calcitonin helps to decrease the level of calcium in the blood. It does this by promoting the deposition of calcium in the bones and inhibiting its release from the bones.

4. **Function of Parathyroid Hormone**:
- Parathyroid Hormone increases the level of calcium in the blood. It achieves this by stimulating the release of calcium from the bones, increasing calcium reabsorption in the kidneys, and promoting the activation of vitamin D, which enhances calcium absorption in the intestines.

5. **Antagonistic Relationship**:
- Calcitonin and Parathyroid Hormone have opposing effects on calcium levels in the blood. While Calcitonin lowers calcium levels, Parathyroid Hormone raises them. This antagonistic relationship helps maintain calcium homeostasis in the body.

6. **Regulation of Phosphorus**:
- Parathyroid Hormone also decreases the level of phosphate in the blood, while Calcitonin does not have a significant effect on phosphate levels. Thus, PTH plays a crucial role in regulating both calcium and phosphorus levels.

**Final Answer**: The two hormones responsible for the regulation of calcium and phosphorus in the blood are Calcitonin (from the Thyroid Gland) and Parathyroid Hormone (from the Parathyroid Gland).

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