**Core Concept**
Adrenal suppression occurs when the body's natural production of cortisol and aldosterone is inhibited by long-term administration of glucocorticoids, such as prednisone. This can lead to a reliance on exogenous steroids for both glucocorticoid and mineralocorticoid effects.

**Why the Correct Answer is Right**
The correct answer is related to the concept of adrenal insufficiency, which can occur when the adrenal glands do not produce sufficient amounts of cortisol and aldosterone. Glucocorticoids, such as prednisone, can suppress the production of these hormones by the adrenal glands, leading to a decrease in their production. This can cause symptoms such as fatigue, weight loss, and hypotension. The hypothalamic-pituitary-adrenal (HPA) axis is responsible for regulating the production of cortisol and aldosterone, and glucocorticoids can disrupt this axis, leading to adrenal insufficiency.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because adrenal suppression due to steroid therapy does not typically cause hyperglycemia, as the body's natural production of cortisol is not responsible for glucose regulation.

**Option B:** This option is incorrect because adrenal suppression due to steroid therapy does not typically cause hyperkalemia, as the body's natural production of aldosterone is responsible for potassium regulation.

**Option C:** This option is incorrect because adrenal suppression due to steroid therapy can actually cause hypokalemia, not hyperkalemia, due to the suppression of aldosterone production.

**Clinical Pearl / High-Yield Fact**
It's essential to note that patients on long-term steroid therapy should be tapered off the medication gradually to avoid adrenal crisis, a life-threatening condition that occurs when the adrenal glands are unable to produce sufficient amounts of cortisol.

**Correct Answer:** C.