Summary–The lab tests commonly used to screen for adrenal diseases are: serum cortisol level, serum ACTH level, serum DHEA level, serum aldosterone level, serum renin level, and serum metanephrine and normetanephrine.
The adrenal glands (there are two, one located on the top of each kidney) secrete homones into the blood that are active throught out the body.
The adrenal glands secrete three different hormones: cortisol, aldosterone, and catecholamines (epinephrine and norepinephrine).
Addison’s Disease means underactive adrenal glands (adrenal insufficiency) that fail to secrete sufficient amounts of cortisol, aldosterone, and adrenal androgens. Addison’s disease is uncommon and the symptoms are weakness, fatigue, decreased appetite, abdominal pain, diarrhea, muscle and joint pain, and absent menses.
Severe adrenal insufficiency can lead to dangerously low blood pressure and if suspected is treated with immediate IV hydrocortisone and IV saline fluid loading.
To diagnose Addison’s disease we can order an 8 am morning serum cortisol (a serum cortisol of less than 3 micrograms/deciliter is diagnostic especially when accompanied by an elevated serum ACTH level of above 200 picograms per ml. If the serum DHEA (an adrenal androgen) is above 1000 nanograms per ml, the patient does not have adrenal insufficiency. (1)
Cushing’s syndrome means an excessive amount of cortisol and/or chemicals related to cortisol (for example medicines like prednisone, prednisolone, or dexamethasone).
The most common cause of Cushing’s syndrome is medically prescribed cortisol-like drugs (eg, prednisone).
Cushing syndrome can be due to over production of cortisol by the adrenal glands. It is very uncommon with two or three new cases per year for every one million persons. (2)
The symptoms of Cushing’s syndrome include high blood pressure, central obesity, weakness, acne, and elevated blood sugar. These symptoms are all very common but are rarely due to Cushing’s syndrome because it is so uncommon.
The best screening test for Cushing’s Syndrome is dexamethasone suppression test. The patient is given one milligram of dexamethasone by mouth at 11 pm and the next morning at 8 am a serum cortisol level is drawn. If the am serum cortisol is supressed then the patient does not have Cushing’s Syndrome (the actual numbers for the serum cortisol depend on the method the laboratory uses to run the test).
Rarely, a person can have a normal dexamethasone supression test when Cushing’s Syndrome is caused by a pituitary problem—if a pituitary gland cause of Cushing’s Syndrome is suspected then a 24 hour urine for free cortisol is ordered.
The adrenal gland can overproduce the hormone aldosterone. Overproduction of aldosterone is a common cause of high blood pressure (being the cause of perhaps 5 to 10% of hypertension).
Adrenal overproduction of aldosterone as a cause of high blood pressure is screened for with a serum aldosterone level and a serum renin level.
An adrenal gland pheochromocytoma can overproduce epinephrine and norepinephrine and lead to severe high blood pressure. Pheochromocytoma is a very rare cause of hypertension. However, if it is suspected, it can be screened for with plasma metanephrine and normetanephrine (we use these instead of measuring epinephrine and norepinephrine for technical reasons).
If the metanephrine and normetanephrine levels are normal (not elevated), then pheochromocytoma is ruled out.
(1) Current Medical Diagnosis and Treatment 2011. Chapter 26, Endocrine Disorders
(2) The Diagnosis of Cushing’s Syndrome: an Endocrine Society Clinical Practice Guideline available at https://www.endo-society.org/guidelines/final/upload/Cushings_Guideline.pdf.