Cushing’s disease is caused by hyperactivity of 

Options

A. GH
B. Thyroxine
C. Insulin
D. Glucocorticoids/Cortisol.

Answer

### Step-by-Step Solution:

1. **Understanding Cushing's Disease**: Cushing's disease is a condition characterized by excessive levels of cortisol in the body. It is important to identify which hormone is responsible for this condition.

2. **Identifying the Hormones**: The options provided are:
- Growth Hormone (GH)
- Thyroxin
- Insulin
- Glucocorticoids (Cortisol)

3. **Analyzing Each Option**:
- **Growth Hormone (GH)**: Secreted by the anterior lobe of the pituitary gland, it primarily stimulates growth and metabolism but is not related to Cushing's disease.
- **Thyroxin**: Produced by the thyroid gland, it regulates metabolism and oxygen consumption but does not cause Cushing's disease.
- **Insulin**: Secreted by the pancreas, it regulates glucose levels in the blood and is not associated with Cushing's disease.
- **Glucocorticoids (Cortisol)**: Secreted by the adrenal cortex, cortisol is involved in carbohydrate metabolism and the regulation of various bodily functions.

4. **Conclusion**: The hyperactivity of glucocorticoids, specifically cortisol, leads to Cushing's disease. The overproduction of cortisol results in various symptoms, including fat deposition in specific areas of the body.

5. **Final Answer**: Cushing's disease is caused by hyperactivity of glucocorticoids (cortisol).