**Core Concept**
Aldosterone is a steroid hormone produced by the adrenal cortex, playing a crucial role in regulating electrolyte balance and blood pressure. It promotes sodium retention and potassium excretion in the kidneys, which in turn affects blood volume and pressure.

**Why the Correct Answer is Right**
Excess aldosterone leads to increased sodium reabsorption, resulting in water retention and subsequent hypertension. This is due to the activation of the mineralocorticoid receptor (MR) in the collecting ducts of the kidneys, which stimulates the reabsorption of sodium ions. The increased sodium reabsorption also leads to increased potassium excretion, resulting in hypokalemia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as excess aldosterone is indeed associated with hypokalemia, not hyperkalemia. The increased potassium excretion in the urine due to aldosterone excess leads to hypokalemia.
**Option B:** This option is incorrect as hypertension is a well-established consequence of excess aldosterone. The increased sodium reabsorption and water retention lead to increased blood volume and pressure.
**Option C:** This option is incorrect as metabolic alkalosis is a common consequence of excess aldosterone. The increased potassium excretion leads to a decrease in hydrogen ion excretion, resulting in metabolic alkalosis.

**Clinical Pearl / High-Yield Fact**
A classic exam trap is to remember that "Aldosterone causes Hypokalemia, Hypertension, and Metabolic Alkalosis" - a mnemonic that helps to recall the key effects of excess aldosterone.

**Correct Answer:** D.