Cortisol (COR) in the evening

Cortisol (COR) – is the main glucocorticoid produced in the adrenal cortex. Cortisol concentration is most commonly measured to diagnose diseases caused by excessive cortisol production during Cushing's syndrome, adrenal steroid deficiency during Addison's disease, and for treatment monitoring. Increased serum concentrations are found during stress response, psychiatric disorders, obesity, diabetes, alcoholism, and pregnancy, which can cause diagnostic challenges in Cushing's syndrome. Low cortisol concentration is found in patients with rare adrenal enzyme deficiencies and those experiencing long-term stress. Normally, the highest cortisol secretion occurs in the second half of the night, with the cortisol concentration peaking in the early morning. After that, the cortisol concentration begins to fall during the day, reaching the lowest concentration in the first half of the night. Therefore, when taking cortisol samples, circadian variations in cortisol secretion and the effects of stress need to be considered.