Cortisol test: what it shows, in blood, saliva, and urine

A referral for a cortisol test often raises more questions than the procedure itself: the result depends on the time of day the blood is drawn. Below is what the test shows, how blood, saliva, and 24-hour urine tests differ, and how to read the numbers on the report form.

What cortisol is and what the test shows

Cortisol is a steroid hormone (a glucocorticoid) produced in the adrenal cortex. Its synthesis follows a chain: the hypothalamus releases corticotropin-releasing hormone, which signals the pituitary gland to release ACTH, and ACTH stimulates cortisol; a rise in cortisol reduces the secretion of corticotropin-releasing hormone and ACTH through negative feedback.

The hormone affects blood pressure, protein, fat, and carbohydrate metabolism, immune function, and the nervous system. It has a characteristic daily rhythm: lowest in the evening, highest in the morning; in women, levels also change with the stages of the menstrual cycle.

The test shows the hormone level at the time of collection and helps determine whether too much or too little is being produced.

Blood cortisol test

A blood sample is needed; it is usually requested in the morning. The day before, you may be asked to avoid intense exercise, and your doctor may ask you to temporarily stop medications that affect the result (anticonvulsants, estrogens, synthetic glucocorticoids — hydrocortisone, prednisone, prednisolone, androgens).

Reference ranges depend on the time of day and the clinical situation, and ranges differ slightly between laboratories.

Cortisol in saliva and urine

In addition to blood, cortisol can be measured in urine or saliva.

Dexamethasone test

This is a suppression test: it is performed in the morning after taking dexamethasone the day before as prescribed by a doctor. The expected result may fall outside the usual range — it is assessed according to the rules of the specific test.

When a doctor orders a cortisol test

The main reasons are to check for increased or decreased cortisol production and to assess pituitary and adrenal function: the test is part of the workup when Cushing's syndrome and Addison's disease are suspected. It is also ordered for acute adrenal insufficiency (a life-threatening condition caused by cortisol deficiency), sepsis, and low blood pressure.

The following signs can help suspect Cushing's syndrome:

• more fat on the neck, upper back, chest, and abdomen, while the arms and legs look thin;
• a red, round face, skin that bruises easily, stretch marks on the abdomen, thighs, chest, and under the arms;
• muscle weakness, especially in the upper arms and legs;
• decreased libido, irritability, anxiety, depressed mood, irregular periods or their cessation, and excessive hair growth.

The syndrome is more common in women; it is rare in children, and in that case the main signs are obesity and stunted growth. With high cortisol, the patient is referred to an endocrinologist, and further tests and examinations of the brain and kidneys may follow.

What high and low cortisol mean

An elevated level occurs in Cushing's syndrome (the pituitary produces too much ACTH due to tissue overgrowth or a tumor), in ectopic syndrome (a tumor outside the pituitary or adrenal glands produces a lot of ACTH), in an adrenal tumor, and with stress and acute illness.

A decreased level is possible in Addison's disease (the adrenal glands do not produce enough cortisol), in hypopituitarism (the pituitary does not signal the adrenal glands), and when their function is suppressed by glucocorticoid medications — oral drugs, creams, drops, inhalers, injections, and chemotherapy.

The most common source of excess is long-term use of high doses of steroids, such as hydrocortisone or prednisolone; less commonly, benign overgrowth in the pituitary or adrenal glands. Without treatment, heart attack and stroke, high blood pressure, type 2 diabetes, risk of blood clots, osteoporosis, and kidney stones are possible.

High or low cortisol alone is not a reason to call an ambulance. Call 103 or 112 — if a heart attack or stroke is suspected, or acute adrenal insufficiency (a life-threatening condition caused by cortisol deficiency).

This material is for reference and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer