Hypercortisolism is a phenomenon identified in traditional medicine for Cushing's syndrome, an endocrine disease, but is commonly discovered during clinical evaluation in functional medicine. Endogenous Cushing's syndrome itself is an uncommon disease, but if not properly evaluated, it can cause various complications in patients, so early detection and treatment are important. Additionally, pseudo-Cushing's syndrome, which may appear to be Cushing's syndrome, is often closely related to mental illness and stress reactions. As a functional medicine physician, it is important to understand cortisol metabolism and testing methods to evaluate hypercortisolism, and it is necessary to consider various patient’s conditions and solutions when hypercortisolism is confirmed.