What is the significance of an adrenocorticotropic hormone (ACTH) stimulated cortisol level of 18.8, indicating elevated cortisol, specifically hypercortisolemia?

From the Guidelines

An ACTH-stimulated cortisol level of 18.8 μg/dL is above the threshold for adrenal insufficiency, suggesting that the adrenal glands are producing an adequate amount of cortisol in response to stimulation. According to the Endocrine Society guidelines, a peak cortisol level above 18 μg/dL at 30 or 60 minutes after ACTH stimulation indicates normal adrenal function 1. This level suggests that the adrenal glands are responding appropriately to the ACTH stimulation test. However, interpretation of this result depends on several factors, including the time of day the sample was collected, whether the patient was fasting, and any medications they may be taking.

Some key points to consider when interpreting this result include:

• The timing of the sample collection: cortisol levels typically follow a circadian rhythm, with highest levels in the morning and lowest levels at night.
• The patient's clinical situation: symptoms such as fatigue, weight loss, or hypotension may suggest adrenal insufficiency, even with a normal cortisol level.
• The presence of any medications that may affect cortisol levels: certain medications, such as corticosteroids, can suppress cortisol production.

It is essential to discuss these results with a healthcare provider who can interpret them in the context of the patient's overall health status and any symptoms they may be experiencing. The healthcare provider may consider additional testing or evaluation to determine the underlying cause of any symptoms or abnormalities. In patients with suspected adrenal insufficiency, education on stress dosing for sick days, use of emergency steroid injectables, and when to seek medical attention for impending adrenal crisis is crucial 1.

In the context of Cushing's disease, a cortisol level of 18.8 μg/dL may be considered elevated, and treatment options such as medication or surgery may be considered 1. However, the management of Cushing's disease is complex and requires a comprehensive evaluation of the patient's clinical situation and laboratory results.

Overall, an ACTH-stimulated cortisol level of 18.8 μg/dL is generally considered normal, but interpretation depends on the individual patient's clinical situation and laboratory results. A healthcare provider should be consulted to determine the best course of action and to develop a personalized treatment plan.

From the Research

Significance of Elevated Cortisol Levels

• An adrenocorticotropic hormone (ACTH) stimulated cortisol level of 18.8 indicates elevated cortisol, specifically hypercortisolemia 2, 3.
• Elevated cortisol levels are associated with various health issues, including osteoporosis, hypertension, diabetes mellitus, susceptibility to infections, and depression 3.
• High cortisol levels may also protect against chronic obstructive pulmonary disease, but this association is complex and requires further study 3.

Diagnostic Tests for Cushing's Syndrome

• The high-dose dexamethasone suppression test is a mainstay in the differential diagnosis of Cushing's syndrome, with urine free cortisol being a useful endpoint 2, 4.
• The test involves administering a high dose of dexamethasone and measuring the suppression of cortisol secretion, with a suppression of greater than 90% indicating pituitary disease 4.
• The 1-mg dexamethasone suppression test is also effective in detecting autonomous cortisol secretion by a clinically inapparent adrenal adenoma, with cortisol levels greater than 138 nmol/l indicating a high post-test probability of adrenal functional autonomy 5.

Relationship Between Cortisol Levels and Mortality

• High salivary cortisol levels are associated with increased mortality risk in a general older population, with men having a higher mortality risk than women 3.
• The relationship between cortisol levels and mortality is complex and may be influenced by various factors, including the presence of chronic diseases and the use of glucocorticoids 3, 6.

Measurement of Cortisol Levels

• Salivary cortisone measurement is a convenient and reliable method for assessing cortisol levels, with a strong correlation between salivary cortisone and serum cortisol after dexamethasone suppression 6.
• The overnight dexamethasone suppression test with measurement of salivary cortisone has potential as a first-line test for suspected Cushing's syndrome, with 100% sensitivity and reasonable specificity 6.