The adrenal gland consists of a medulla that produces catecholamines and a cortex that produces steroid hormones, both components having specific functions and regulations within the endocrine system. Hyperfunction of the adrenal gland is caused by the excessive secretion of a certain hormone, which can lead to conditions such as hyperaldosteronism, which causes hypertension and hypokalemia due to excess aldosterone, or Cushing's syndrome, which is the result of long-term elevated cortisol levels, and is manifested by symptoms such as weight gain, muscle weakness and high blood pressure. Adrenal hypofunction can be caused by primary, secondary or tertiary insufficiency, with possible serious complications such as adrenal crisis, while hypoaldosteronism causes a lack of aldosterone, and Addison's disease, often autoimmune, is characterized by a gradual onset. Cortisol, a stress hormone that is synthesized from cholesterol in the adrenal glands, secreted in a circadian rhythm, regulated through a negative feedback loop is crucial for energy metabolism, electrolyte balance and affects the immune system, and its metabolism takes place through conversion into cortisone and further metabolism. 40 samples of 24h urine from patients aged 25 - 83 (30 women, 10 men) were analyzed with two methods of measuring cortisol concentration by electrochemiluminescence immunoassay (ECLIA) on Cobas devices manufactured by Roche Diagnostics, with statistical data processing using "MedCalc" software. The research analyzed the data distribution and compared the two methods using the Kolmogorov-Smirnov test and the Passing-Bablok regression. The first method, which includes sample extraction, has no significant deviation from the normal distribution, while the second method, without extraction, showed a significant deviation from the normal distribution. The regression results show a significant proportional difference between the methods, with the method involving sample extraction giving consistently higher values. However, the systematic difference between the methods is not significant and the high correlation suggests the consistency of the methods despite the proportional differences. The conclusion of the research highlights significant differences between the two methods for measuring cortisol in urine. Despite the proportional differences, the high correlation between the methods indicates the consistency of the measurements. These findings emphasize the need for careful understanding of method specificity and calibration when interpreting results.