**Core Concept**
Glucocorticoid deficiency is a condition characterized by inadequate production of cortisol, a vital glucocorticoid hormone produced by the adrenal cortex. Cortisol plays a crucial role in regulating metabolism, immune response, and stress response in the body.

**Why the Correct Answer is Right**
Glucocorticoid deficiency typically presents with features such as weight loss, fatigue, and hypoglycemia due to impaired gluconeogenesis and glycogenolysis. The deficiency also impairs the body's ability to respond to stress, leading to decreased ability to fight infections. Additionally, patients with glucocorticoid deficiency may exhibit hyperpigmentation, hypotension, and decreased libido.

**Why Each Wrong Option is Incorrect**
**Option A:** Hyperkalemia is a feature of primary aldosteronism, not glucocorticoid deficiency. Glucocorticoids help regulate potassium levels by promoting its excretion in the urine.
**Option B:** Hypertension is not a feature of glucocorticoid deficiency; in fact, patients may experience hypotension due to vasodilation and decreased vascular tone.
**Option C:** Hyperglycemia is a feature of glucocorticoid excess, not deficiency. Glucocorticoids stimulate gluconeogenesis and glycogenolysis, leading to increased blood glucose levels.

**Clinical Pearl / High-Yield Fact**
Glucocorticoid deficiency can be caused by primary adrenal insufficiency (Addison's disease), secondary adrenal insufficiency (due to pituitary or hypothalamic disorders), or iatrogenic causes (e.g., long-term glucocorticoid use).

**Correct Answer:** C. Hyperglycemia