From the Guidelines
A slightly elevated morning cortisol level with a normal ACTH level typically does not require immediate further testing, especially if the elevation is mild and the patient has no symptoms. This pattern suggests that the adrenal glands may be producing slightly more cortisol than normal, but the pituitary gland (which produces ACTH) is responding appropriately by not stimulating additional cortisol production. Common causes for this finding include stress, obesity, depression, alcoholism, or certain medications like oral contraceptives or estrogen 1. However, if the patient has symptoms suggestive of cortisol excess (such as weight gain, fatigue, muscle weakness, high blood pressure, or easy bruising), or if the cortisol elevation is significant, additional testing would be warranted. In such cases, a 24-hour urinary free cortisol test or an overnight dexamethasone suppression test could help determine if there is true hypercortisolism, as suggested by the guidelines for diagnosis and management of Cushing's disease 1.
Some key points to consider in the diagnosis and management of Cushing's syndrome include:
- Clinical suspicion for Cushing's syndrome (CS) should be based on symptoms and signs, and further testing should be guided by the clinical likelihood of endogenous CS 1
- A normal response to the overnight 1-mg dexamethasone suppression test (DST) is a serum cortisol < 1.8 μg/dL (50 nmol/L) at 0800 h in the morning after 1 mg dexamethasone given between 2300 h and midnight 1
- Monitoring response to medical therapy should include measures of cortisol, patient symptoms, and comorbidities, especially weight, glycemia, and blood pressure, as well as quality of life (QoL) 1
It's also reasonable to repeat the morning cortisol measurement after ensuring proper collection conditions, as cortisol levels can fluctuate naturally and are affected by sleep patterns, recent exercise, and acute stress. If the patient's cortisol level is only slightly elevated, as in this case (19.8), and the patient has no symptoms, no further testing is immediately required, but the patient should be monitored for any changes in symptoms or cortisol levels over time 1.
From the Research
Evaluation of Morning Cortisol and ACTH Levels
- A morning cortisol level of 19.8 is considered slightly elevated, while an ACTH level of 17.9 is within the normal range.
- According to 2, a mean basal morning serum cortisol of > or = 300 nmol/L excludes the possibility of adrenal insufficiency, and a level of < 110 nmol/L suggests adrenal insufficiency.
- However, the provided cortisol level of 19.8 does not directly correspond to the units used in the study (nmol/L), making it difficult to draw a direct comparison.
Further Testing Requirements
- The study 3 suggests that the overnight dexamethasone suppression test can be used to diagnose Cushing's syndrome, but it may not be necessary for patients with normal ACTH levels and slightly elevated morning cortisol levels.
- Another study 4 found that a serum cortisol level greater than 2 micrograms/dL after dexamethasone suppression is indicative of Cushing's syndrome, but the provided cortisol level of 19.8 does not directly correspond to the units used in the study (micrograms/dL).
- The study 5 recommends using a cut-off point of 80 nM (3 microg/dL) for normal suppression in the overnight dexamethasone suppression test, but again, the units do not match the provided cortisol level.
Considerations for Next Steps
- Given the slightly elevated morning cortisol level and normal ACTH level, further testing may be necessary to rule out Cushing's syndrome or other adrenal disorders.
- A dexamethasone suppression test, as described in 3, 6, and 5, could be considered to evaluate the cortisol response to dexamethasone suppression.
- However, the decision to proceed with further testing should be based on a comprehensive evaluation of the patient's clinical presentation, medical history, and laboratory results.