The diagnosis of Cushing's syndrome primarily involves testing cortisol levels, adrenocorticotropic hormone (ACTH) levels, and a dexamethasone suppression test. Cortisol is the core diagnostic indicator for Cushing's syndrome, and elevated levels are a major characteristic of the disease. ACTH testing helps differentiate between pituitary, ectopic ACTH syndrome, and adrenal-derived Cushing's syndrome. The dexamethasone suppression test assesses the ability to suppress cortisol secretion, helping to clarify the cause. Diagnosis of Cushing's syndrome requires a combination of clinical symptoms and laboratory test results, and imaging studies may be necessary to locate the lesion.
1. Cortisol Testing: Cortisol is a key indicator for the diagnosis of Cushing's syndrome, and is usually assessed through 24-hour urinary free cortisol, serum cortisol, or salivary cortisol testing. 24-hour urinary free cortisol testing is the most commonly used method, reflecting cortisol secretion throughout the day. Serum cortisol testing typically requires sampling in the morning and evening to observe whether the diurnal rhythm of cortisol is normal. Salivary cortisol testing is a non-invasive method suitable for long-term monitoring.
2. Adrenocorticotropic hormone (ACTH) testing: ACTH testing helps differentiate between different causes of Cushing's syndrome. Patients with pituitary Cushing's syndrome typically have elevated or normal ACTH levels, while those with ectopic ACTH syndrome have significantly elevated ACTH levels. Patients with adrenal Cushing's syndrome typically have decreased ACTH levels. ACTH testing results need to be combined with other examination findings for comprehensive analysis.
3. Dexamethasone Suppression Test: The dexamethasone suppression test is a commonly used method to assess the ability to suppress cortisol secretion. A low-dose dexamethasone suppression test is used to screen for Cushing's syndrome, while a high-dose dexamethasone suppression test is used to differentiate between pituitary-derived and ectopic ACTH syndrome. Abnormal test results suggest that cortisol secretion is not suppressed, supporting the diagnosis of Cushing's syndrome.
4. Imaging examinations: Imaging examinations are used to locate the lesion site in Cushing's syndrome. Pituitary MRI is the preferred method for diagnosing pituitary Cushing's syndrome and can detect pituitary microadenomas. Chest CT or MRI is used to rule out ectopic ACTH syndrome, while adrenal CT or MRI is used to evaluate adrenal lesions. Imaging examinations should be combined with laboratory test results for a comprehensive judgment.
5. Other auxiliary examinations: The diagnosis of Cushing's syndrome also requires consideration of clinical symptoms and other auxiliary examination results. Common symptoms include central obesity, hypertension, diabetes, and osteoporosis. Other auxiliary examinations, such as serum potassium, blood glucose, and bone mineral density tests, can also help assess the severity of the condition and the presence of complications.
Diagnosing Cushing's syndrome requires a comprehensive evaluation using multiple indicators and testing methods, including cortisol, ACTH, dexamethasone suppression tests, and imaging studies. Through a thorough assessment, doctors can identify the cause and develop a personalized treatment plan. Early diagnosis and timely treatment are crucial for improving patient prognosis; patients are advised to seek medical attention as soon as possible for a detailed examination upon experiencing related symptoms.