Cortisol (COR) in the morning

Cortisol (COR) is the main glucocorticoid produced in the adrenal cortex. Cortisol concentration is most often tested in the diagnosis of diseases caused by excessive cortisol production during Cushing's syndrome, adrenal steroid deficiency during Addison's disease, and treatment monitoring. Increased concentration in serum is detected 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 prolonged stress. Normally, the highest cortisol secretion occurs in the second half of the night, with the cortisol concentration peak reached early in the morning. After that, cortisol concentration begins to decline during the day, reaching its lowest concentration in the first half of the night. Therefore, when taking cortisol samples, circadian variations in cortisol secretion and the effects of stress should be taken into account.