**Core Concept**
Adrenal insufficiency refers to the inadequate production of cortisol and/or aldosterone hormones by the adrenal glands. This condition can lead to various electrolyte and metabolic disturbances due to the imbalance of these crucial hormones.

**Why the Correct Answer is Right**
Adrenal insufficiency is characterized by the deficiency of aldosterone, which regulates sodium and potassium levels. The lack of aldosterone leads to an inability to retain sodium and water, resulting in hyponatremia (Option A). Additionally, the decreased level of cortisol impairs gluconeogenesis, leading to hypoglycemia (Option C). However, the absence of aldosterone does not directly cause metabolic alkalosis (Option D), as aldosterone primarily affects potassium levels, and its deficiency is associated with hypokalemia, not alkalosis. Furthermore, the kidneys compensate for the lack of aldosterone by increasing hydrogen ion excretion, which would lead to metabolic acidosis, not alkalosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Hyponatremia is actually associated with adrenal insufficiency due to the inability to retain sodium and water.
**Option B:** Hyperkalemia is not directly associated with adrenal insufficiency, but hypokalemia is a more common finding due to the lack of aldosterone's potassium-wasting effect.
**Option C:** Hypoglycemia is indeed associated with adrenal insufficiency due to impaired gluconeogenesis and increased glucose utilization.

**Clinical Pearl / High-Yield Fact**
Adrenal insufficiency can be remembered as "salt-wasting" due to the inability to retain sodium and water, leading to hyponatremia and hypovolemia. This is in contrast to mineralocorticoid excess, which can cause hypertension and hypokalemia.

**✓ Correct Answer: D. Metabolic alkalosis**