Urine cortisol measurement is the preferred screening test for Cushing's syndrome and for the diagnosis of pseudo-hyperaldosteronism.
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Cortisol is a steroid hormone released from the adrenal cortex when stimulated by the secretion of the adrenocorticotropic hormone (ACTH) from the anterior pituitary gland. Most of the blood circulating cortisol is bound to the globin binding cortisol and albumin. Less than 5 to 10% of total cortisol in the blood circulates "free" or unconjugated, thus filtering through the kidneys into the urine.
Although urinary cortisol may be less than 5% of circulating cortisol, the amount of filtration follows the pattern of cortisol secretion from the adrenal cortex. As cortisol is secreted on a daily basis, a 24-hour urine sample contains cortisol at both the peak of its secretion and at its lower secretion point and thus constitutes a more accurate (than its blood measurement) for diagnosis or exclusion of Cushing's syndrome, in which high levels of cortisol are constantly secreted.
Possible Interpretations of Pathological Values
- Increase: Amenorrhea, Cushing's syndrome, hyperthyroidism, (small cell) lung cancer, pituitary tumors, pregnancy, stress. Medications: Corticotropin, amphetamines, estrogens, nicotine, contraceptives, spironolactone, synthetic glucocorticoids (prednisone, prednisolone)
- Decrease: Hypothyroidism, renal glomerular dysfunction. Medications: Dexamethasone, inhaled glucocorticoids for the treatment of asthma. Consumption of grapefruit juice.
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
