Professional and Linguistic Assessments Board (PLAB) Practice Exam

What distinguishes Cushing's disease from Cushing's syndrome?

1. Cushing's syndrome is always caused by a pituitary adenoma

2. Cushing's disease involves a pituitary adenoma secreting ACTH

3. Both are caused by adrenal tumors

4. Cushing's disease does not present metabolic issues

The correct answer is: Cushing's disease involves a pituitary adenoma secreting ACTH

Cushing's disease specifically refers to a form of Cushing's syndrome that is caused by a pituitary adenoma producing adrenocorticotropic hormone (ACTH). This excess ACTH stimulates the adrenal glands to produce more cortisol, leading to the symptoms associated with Cushing's syndrome. While Cushing's syndrome encompasses all conditions resulting in excessive cortisol levels—whether due to pituitary adenomas, adrenal tumors, or ectopic ACTH secretion—Cushing's disease is strictly a subset linked to the pituitary. This distinction is crucial in clinical practice, as treatment approaches may differ based on the underlying cause of the syndrome. In contrast, other options describe conditions or facts about Cushing's syndrome and disease that are incorrect or misleading. For example, Cushing's syndrome is not solely caused by a pituitary adenoma, as it can result from various other sources of excess cortisol. Furthermore, stating that both are caused by adrenal tumors neglects the broader range of potential etiologies for Cushing's syndrome. Lastly, implying that Cushing's disease does not present metabolic issues overlooks the reality that both conditions typically lead to similar metabolic complications due to elevated cortisol levels.