Final answer:
The most common cause of Cushing's syndrome is long-term exposure to excess glucocorticoids, typically due to the hypersecretion of cortisol often caused by a pituitary tumor.
Step-by-step explanation:
Long-term exposure to excess glucocorticoids is the most common cause of Cushing's syndrome.
Cushing's syndrome is associated with the hypersecretion of cortisol, a corticosteroid hormone produced by the adrenal cortex in response to long-term stress. This condition can manifest through a variety of symptoms including obesity, diabetes, high blood pressure, excessive body hair, osteoporosis, depression, the appearance of stretch marks on the skin, and a characteristic moon face where fat deposits give the face a rounded appearance. The most frequent cause of the syndrome is a pituitary tumor that overproduces adrenocorticotropic hormone (ACTH), prompting the adrenal cortex to release excessive amounts of cortisol.
Treatment for Cushing's syndrome often involves surgery to remove the tumor or medications to suppress adrenal gland activity. In contrast, Addison's disease results from the hyposecretion of glucocorticoids and possibly mineralocorticoids, typically due to autoimmune issues or damage from infections like tuberculosis.