Cortisol (COR) in the morning

Cortisol (COR) – is the main glucocorticoid produced in the adrenal cortex. Cortisol concentration is most often tested when diagnosing diseases caused by excessive cortisol production during Cushing's syndrome, adrenal steroid deficiency during Addison's disease, and for treatment monitoring. Increased serum concentration is found during stress response, psychiatric disorders, obesity, diabetes, alcoholism, and pregnancy, which can cause diagnostic difficulties in the case of Cushing's syndrome. Low cortisol concentration is found in patients with rare adrenal enzyme deficiencies and those experiencing long-term stress. Normally, the highest secretion of cortisol is determined in the second half of the night, and the peak of cortisol concentration is reached in the early morning. After that, the concentration of cortisol starts to decrease during the day, and the lowest concentration is reached in the first half of the night. Therefore, when taking cortisol samples, one must consider the circadian variations in cortisol secretion and the effect of stress.