Which of the following statements best describes the clinical difference between Cushing's disease and Cushing's syndrome?

Both Cushing's disease and Cushing's syndrome are exclusively caused by adrenal tumors.

Cushing's disease results from a pituitary tumor causing excess ACTH, whereas Cushing's syndrome is a broader term for excess cortisol from any cause.

Cushing's disease is primarily caused by long-term glucocorticoid use, while Cushing's syndrome is caused only by adrenal tumors.

Cushing's disease results from a tumor causing excess cortisol production, whereas Cushing's syndrome is mainly due to external glucocorticoid administration.