Aldosterone regulates: blood calcium ion levels. blood iodide ion levels. extracellular sodium and potassium ion levels. blood glucose levels.

Aldosterone is a **mineralocorticoid hormone** produced by the **adrenal cortex**. Its primary role involves the regulation of **electrolyte balance** and **blood pressure**. Here's how it interacts with the options you've provided: 1. **Blood Calcium Ion Levels:** - **Incorrect.** Regulation of calcium levels is primarily managed by hormones such as **parathyroid hormone (PTH)** and **calcitonin**, not aldosterone. 2. **Blood Iodide Ion Levels:** - **Incorrect.** Iodide ion levels are regulated mainly in relation to **thyroid hormone synthesis** and iodine intake, not directly by aldosterone. 3. **Extracellular Sodium and Potassium Ion Levels:** - **Correct.** Aldosterone **increases the reabsorption of sodium (Na⁺)** and the **excretion of potassium (K⁺)** in the kidneys. This action helps maintain **blood volume**, **blood pressure**, and **electrolyte balance**. 4. **Blood Glucose Levels:** - **Incorrect.** Blood glucose is primarily regulated by **insulin** and **glucagon**, not aldosterone. **Conclusion:** **Aldosterone regulates **extracellular sodium and potassium ion levels**.