Healthy Volunteers:
Inclusion Criteria:
1. Age ≥ 18 and ≤ 60 years old;
2. Body mass index (BMI) ≥ 18.5 and ≤ 24.9 kg\*m\^-2;
3. No previous history of chronic diseases such as hyperglycemia, hypertension, dyslipidemia, coronary heart disease and stroke;
4. Normal glucose regulation, defined as: fasting blood-glucose \< 5.6 mmol/L, 2-hour blood-glucose after glucose load \< 7.8 mmol/L, and glycated hemoglobin (HbA1c) \< 5.7%.
Exclusion Criteria:
1. Liver or kidney dysfunction, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) or direct bilirubin higher than 1.5 times the upper limit of normal, or serum creatinine \>115 μmol/L;
2. Pregnancy or lactation women, or people with cancer or mental illness;
3. Factors affecting cortisol levels, including hypothalamus-pituitary-adrenal axis disease, autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis, etc.), diagnosed mental disease, Alzheimer's disease, alcoholism (alcohol \> 60 g/d for male, \>40 g/d for women) and corticosteroid therapy in the past 3 months (females with contraceptives or estrogen);
4. Factors affecting saliva collection, such as serious oral problems (oral ulcers, gingival bleeding);
5. Night shift workers, who are awake from 11:00 PM to 7:00 AM;
6. Acute infection (body temperature ≥ 37.3 ℃ or C-reactive protein \> 50 mg/L).
Cases:
Inclusion Criteria:
1. Aged 18 to 80 years old;
2. Patients with suspected Cushing's syndrome or adrenal insufficiency.
Exclusion Criteria:
1. Corticosteroid therapy within the last 6 weeks;
2. Acute infection;
3. Severe oral conditions;
4. Severe liver and kidney dysfunction;
5. Alcoholism, depression, or other psychiatric disorders.
