**Core Concept**
Cushing's disease is a form of Cushing's syndrome caused by excessive production of adrenocorticotropic hormone (ACTH) by the pituitary gland, leading to hypercortisolism. This results in a characteristic set of clinical and biochemical features.

**Why the Correct Answer is Right**
Cushing's disease is characterized by features such as weight gain, particularly in the central trunk and face, purple striae, hypertension, glucose intolerance or diabetes mellitus, and hirsutism in females. The excessive ACTH production stimulates the adrenal glands to produce cortisol, leading to these symptoms. The high levels of cortisol also suppress the production of ACTH, leading to a negative feedback loop.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Cushing's disease is associated with low levels of ACTH due to negative feedback from high cortisol levels, not high levels.
**Option B:** This option is incorrect because Cushing's disease is characterized by features such as weight gain, not weight loss.
**Option C:** This option is incorrect because Cushing's disease is associated with high levels of cortisol, not low levels.

**Clinical Pearl / High-Yield Fact**
One of the key features of Cushing's disease is the presence of purple striae on the abdomen, which are a result of the thinning of the skin due to the high levels of cortisol. This is a classic clinical finding that should raise suspicion for Cushing's disease.

**Correct Answer: A. This option is incorrect because Cushing's disease is associated with low levels of ACTH due to negative feedback from high cortisol levels, not high levels.**