Parathyroid hormone secretion increases in response to

Options

A. increased secretion of insulin
B. a decrease in blood calcium levels
C. increased secretion of parathyroid - releasing hormone from the hypothalamus.
D. increased production of parathyroid - stimulating hormone from the anterior pituitary

Answer

To solve the question about the conditions that increase parathyroid hormone (PTH) secretion, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Parathyroid Hormone (PTH)**:
- PTH is a hormone produced by the parathyroid glands that plays a crucial role in regulating calcium levels in the blood.

2. **Analyzing the Options**:
- **Option 1: Increase secretion of insulin**:
- Insulin primarily regulates glucose levels and does not have a direct effect on PTH secretion. Therefore, this option is incorrect.

- **Option 2: Decrease in blood calcium level**:
- This is the correct option. When blood calcium levels drop, the parathyroid glands respond by increasing the secretion of PTH. This hormone acts to raise calcium levels by stimulating the release of calcium from bones, increasing calcium reabsorption in the kidneys, and enhancing intestinal absorption of calcium.

- **Option 3: Increased secretion of parathyroid releasing hormone from the hypothalamus**:
- While the hypothalamus does influence hormone secretion, it does not directly stimulate PTH secretion. Thus, this option is incorrect.

- **Option 4: Increased production of parathyroid stimulating hormone from the anterior pituitary**:
- There is no parathyroid stimulating hormone produced by the anterior pituitary that affects PTH secretion. This option is also incorrect.

3. **Conclusion**:
- The correct answer is **Option 2: Decrease in blood calcium level**. This condition directly stimulates the parathyroid glands to secrete more PTH, which helps restore calcium levels in the blood.