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 regarding the secretion of parathyroid hormone (PTH), we need to analyze the options provided and understand the physiological role of PTH in the body.

### Step-by-Step Solution:

1. **Understanding Parathyroid Hormone (PTH)**:
- PTH, also known as parathormone, is secreted by the parathyroid glands, which are located behind the thyroid gland.
- Its primary function is to regulate calcium levels in the blood.

2. **Function of PTH**:
- PTH is known as a hypercalcemic hormone, meaning it increases blood calcium levels.
- It does this by stimulating osteoclast activity, which breaks down bone and releases calcium into the bloodstream.

3. **Stimulus for PTH Secretion**:
- The secretion of PTH is primarily regulated by blood calcium levels.
- When blood calcium levels decrease, the parathyroid glands sense this change and secrete PTH to restore calcium levels.

4. **Analyzing the Options**:
- **Option A: Increased secretion of insulin**: This is incorrect. Insulin is involved in glucose metabolism and does not directly influence PTH secretion.
- **Option B: A decrease in blood calcium level**: This is correct. Low blood calcium levels stimulate the secretion of PTH.
- **Option C: Increased secretion of parathyroid releasing hormone from the hypothalamus**: This is incorrect. There is no hormone known as parathyroid releasing hormone.
- **Option D: Increased production of parathyroid stimulating hormone from the anterior pituitary**: This is also incorrect as there is no such hormone that stimulates the parathyroid gland.

5. **Conclusion**:
- The correct answer is **Option B: A decrease in blood calcium level**. This is the primary stimulus for the secretion of parathyroid hormone.