How is Cushing's Syndrome Diagnosed? Cushing's Syndrome is diagnosed with Low Dose Dexamethasone Suppression Test. Cushing's Syndrome is caused when there is excess cortisol, a glucocorticoid hormone secreted by adrenal cortex. Why Random cortisol levels cannot be used to diagnose Cushing's Syndrome? One cannot simply measure random plasma cortisol to make a diagnosis of excess cortisol hormone in the body because cortisol levels fluctuate throughout the day, and can also be altered by other factors like illness and stress. Thus, the diagnosis of Cushing's Syndrome is made with Overnight Dexamethasone Suppression Test. What is overnight low dose dexamethasone test? It is a good outpatient test in which low dose ( 1 milligrams) of Dexamethasone is given at midnight and serum cortisol levels are measured next morning ( at 8 AM) . In normal individuals the midnight dose of dexamethasone suppresses the cortisol levels to <50 nmol/L
How is Cushing's Syndrome Diagnosed?
Cushing's Syndrome is diagnosed with Low Dose Dexamethasone Suppression Test.
Cushing's Syndrome is caused when there is excess cortisol, a glucocorticoid hormone secreted by adrenal cortex.
Why Random cortisol levels cannot be used to diagnose Cushing's Syndrome?
One cannot simply measure random plasma cortisol to make a diagnosis of excess cortisol hormone in the body because cortisol levels fluctuate throughout the day, and can also be altered by other factors like illness and stress.
Thus, the diagnosis of Cushing's Syndrome is made with Overnight Dexamethasone Suppression Test.
What is overnight low dose dexamethasone test?
It is a good outpatient test in which low dose ( 1 milligrams) of Dexamethasone is given at midnight and serum cortisol levels are measured next morning ( at 8 AM) . In normal individuals the midnight dose of dexamethasone suppresses the cortisol levels to <50 nmol/L. But in case of Cushing's Syndrome there is no suppression in the cortisol levels.
Pseudo-Cushing's Syndrome :
There can also be no suppression of cortisol after Low dose dexamethasone suppression test in certain other conditions like depression, alcohol intake, other medications like phenytoin , and obesity.
What is the alternative test to Low Dose Dexamethasone Suppression Test In Diagnosis Of Cushing's Syndrome?
The alternative to low dose dexamethasone suppression test is 24 hours Urinary Free Cortisol test. Normally <280 nmol free cortisol is excreted in urine in 24 hours. If there is increase in amount of total free cortisol excreted in urine in 24 hours, diagnosis of Cushing Disease is made.
What are the causes of Cushing's Syndrome?
Tags: endocrinology, adrenal, Cushing, Internal medicine review notes, Cushing's diagnosis.
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