**Core Concept**
Cushing's disease is a clinical syndrome caused by excess cortisol production, usually due to a pituitary adenoma secreting adrenocorticotropic hormone (ACTH). One of the diagnostic criteria for Cushing's disease is the weight of the adrenal glands, which are typically enlarged in response to chronic ACTH stimulation.

**Why the Correct Answer is Right**
In Cushing's disease, the adrenal glands are hyperplastic and hypertrophic, leading to an increase in their weight. The normal weight range for adrenal glands is around 4-11 grams. However, in cases of Cushing's disease, the adrenal glands can weigh significantly more, typically in the range of 25-40 grams. This is because the chronic exposure to high levels of ACTH stimulates the adrenal cells to proliferate and hypertrophy, resulting in an increase in gland weight. The adrenal glands may also show histological changes such as increased cell size, nuclear pleomorphism, and cytomegaly.

**Why Each Wrong Option is Incorrect**
**Option A:** This weight range is normal for adrenal glands and is not indicative of Cushing's disease.
**Option B:** This weight range is slightly above normal, but not typically seen in Cushing's disease. The adrenal glands in Cushing's disease are usually significantly heavier.
**Option C:** This weight range is still below the typical range seen in Cushing's disease.

**Clinical Pearl / High-Yield Fact**
In cases of Cushing's disease, the adrenal glands are often "hyperplastic" and "hypertrophic", leading to an increase in their weight. This is a critical diagnostic clue that can help differentiate Cushing's disease from other causes of Cushing's syndrome.

**✓ Correct Answer: D. 25-40 gm**