WHAT IS CORTISOL (URINE) TEST?
Cortisol is a steroidal hormone released from the adrenal cortex when stimulated by secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary gland. Free cortisol is unconjugated cortisol filtered by the renal glomeruli into the urine. Although it comprises less than 5% of circulating cortisol, the amount filtered follows the pattern of cortisol secretion from the adrenal cortex. Because it is excreted in a diurnal pattern, a 24-hour urine sample contains the effects of both the peak and trough cortisol levels and is thus a more accurate measurement than serum levels for diagnosing or ruling out Cushing’s syndrome in which continuously high levels of cortisol are secreted.