**Core Concept**
Hyperaldosteronism is a condition characterized by the excessive production of aldosterone, a steroid hormone produced by the adrenal glands that plays a crucial role in regulating electrolyte balance and blood pressure. Aldosterone stimulates the kidneys to retain sodium and water, leading to increased blood volume and pressure.

**Why the Correct Answer is Right**
Aldosterone promotes sodium retention by binding to mineralocorticoid receptors in the collecting ducts of the kidneys, which increases sodium reabsorption and potassium excretion. This leads to increased blood volume and blood pressure. In hyperaldosteronism, the elevated aldosterone levels can cause hypertension, hypokalemia (low potassium levels), and metabolic alkalosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the characteristics of hyperaldosteronism. However, I'll provide an explanation for the sake of completeness.
**Option B:** Hyperaldosteronism is indeed characterized by hypokalemia, which is a direct result of increased potassium excretion in the urine.
**Option C:** This option is incorrect because hyperaldosteronism is associated with hypertension, not hypotension. The excessive sodium retention and water retention lead to increased blood volume and pressure.
**Option D:** Metabolic alkalosis is a characteristic of hyperaldosteronism, which is caused by the increased excretion of hydrogen ions in the urine.

**Clinical Pearl / High-Yield Fact**
In patients with hyperaldosteronism, the combination of hypertension and hypokalemia is a classic clinical presentation. The condition is often caused by an aldosterone-producing adenoma (APA) or familial hyperaldosteronism, and treatment typically involves surgical resection of the adenoma or medical management with spironolactone.

**Correct Answer: B. Hypokalemia.**