The hormone of the adrenal cortex which causes `Na^+` retention and `K^+` excretion is

Options

A. Corticosol
B. Corticosterone
C. Cortisol
D. Aldosterone

Answer

To solve the question regarding the hormone of the adrenal cortex that causes sodium ion (Na^+) retention and potassium ion (K^+) excretion, we can follow these steps:

### Step 1: Identify the Adrenal Cortex Hormones
The adrenal cortex produces several hormones, including:
- Cortisol
- Corticosterone
- Aldosterone

### Step 2: Understand the Function of Each Hormone
- **Cortisol**: Primarily involved in metabolism and stress response, but does not directly regulate Na^+ and K^+ levels.
- **Corticosterone**: Similar to cortisol, it has some effects on metabolism but is not primarily responsible for Na^+ retention and K^+ excretion.
- **Aldosterone**: This hormone specifically regulates sodium and potassium levels in the body.

### Step 3: Focus on Aldosterone
Aldosterone is a mineralocorticoid hormone that:
- Promotes the reabsorption of sodium ions (Na^+) in the kidneys.
- Stimulates the excretion of potassium ions (K^+) from the kidneys into the urine.

### Step 4: Mechanism of Action
Aldosterone acts on mineralocorticoid receptors located in the cells of the distal tubule and collecting duct of the kidneys. It:
- Activates sodium-potassium pumps, which transport 3 Na^+ ions out of the cell into the interstitial fluid and 2 K^+ ions into the cell from the interstitial fluid.
- This action creates a concentration gradient that leads to:
- Increased reabsorption of Na^+ and water into the bloodstream.
- Increased secretion of K^+ into the urine.

### Conclusion
Based on the above analysis, the hormone of the adrenal cortex that causes Na^+ retention and K^+ excretion is **Aldosterone**.

### Final Answer
**Aldosterone** (Option D)

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