Cushing's syndrome is caused by excessive cortisol production and can be difficult to diagnose due to shared symptoms with other conditions. It may be endogenous from pituitary or adrenal tumors, or exogenous from long-term high-dose corticosteroid use. Diagnosis involves ruling out other conditions through tests and assessing cortisol levels in blood and urine over 24 hours. Treatment aims to normalize cortisol levels and depends on the underlying cause, such as surgery to remove tumors or medication to reduce cortisol production. Left untreated, Cushing's syndrome can cause serious health issues.