Which substance is used mainly in kidney function test `:-`

Options

A. Creatinine
B. `Na^(+)`
C. Inulin
D. Urea

Answer

**Step-by-Step Solution:**

1. **Understanding Kidney Function Tests**: Kidney function tests are essential for assessing how well the kidneys are working. They typically measure substances in the blood and urine to evaluate kidney health.

2. **Types of Kidney Function Tests**: There are two main types of tests mentioned:
- **Albumin-to-Creatinine Ratio (ACR)**: This test measures the amount of albumin (a protein) in the urine compared to creatinine, which helps assess kidney damage.
- **Glomerular Filtration Rate (GFR)**: This test estimates how well the kidneys filter blood.

3. **Identifying the Key Substances**: In the context of GFR, two substances are often discussed:
- **Creatinine**: This is a common endogenous marker for estimating GFR.
- **Inulin**: This is considered the gold standard for measuring GFR due to its specific properties.

4. **Properties of Inulin**: Inulin is preferred because:
- It is not reabsorbed by the kidneys.
- It is freely filtered by the glomeruli.
- It is not synthesized or metabolized by the kidneys, making it an accurate measure of kidney function.

5. **Conclusion**: Based on the properties and usage in kidney function tests, the substance that is mainly used for kidney function tests, particularly for measuring GFR, is **Inulin**.

**Final Answer**: The substance used mainly in kidney function tests is **Inulin**.

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