**Core Concept**
Cushing's disease is a rare endocrine disorder caused by excess cortisol production due to a pituitary adenoma secreting adrenocorticotropic hormone (ACTH), leading to various clinical and biochemical manifestations.

**Why the Correct Answer is Right**
Cushing's disease is characterized by features such as weight gain, particularly in the trunk and face, buffalo hump, purple striae, hypertension, glucose intolerance or diabetes mellitus, and osteoporosis. These symptoms result from the prolonged exposure to excess cortisol, which affects multiple body systems.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is actually a feature of Cushing's disease. Excess cortisol production leads to weight gain, particularly in the trunk and face.
* **Option B:** This option is incorrect because it is also a feature of Cushing's disease. Purple striae are a result of skin thinning and fragility due to cortisol excess.
* **Option C:** This option is incorrect because it is a feature of Cushing's disease. Hypertension is a common finding in patients with Cushing's disease due to the mineralocorticoid effects of cortisol.
* **Option D:** This option is incorrect because it is not a feature of Cushing's disease. Patients with Cushing's disease may actually experience hypokalemia due to mineralocorticoid effects, but this is not a typical feature.

**Clinical Pearl / High-Yield Fact**
Cushing's disease is often associated with a "moon face" appearance, which is a characteristic clinical finding due to the redistribution of fat in the face.

**Correct Answer: D. Hypokalemia**