Cortisol

Test description

Cortisol is the main stress hormone secreted by the adrenal cortex. It regulates blood glucose levels, blood pressure, water-electrolyte balance, inflammatory response, and the sleep-wake cycle. Its secretion follows a distinct circadian rhythm: it peaks in the morning hours, with the lowest values occurring late in the evening – therefore, a reliable test requires sampling between 7:00 and 10:00 AM. Chronically elevated cortisol accompanies long-term stress, overtraining, and sleep disorders. It can manifest as insomnia despite fatigue, accumulation of abdominal and facial fat, increased blood pressure and glucose, decreased immunity, irritability, and muscle mass loss. Very high values require the exclusion of Cushing's syndrome. Conversely, excessively low cortisol causes extreme weakness, drops in blood pressure and dizziness upon standing, cravings for salty foods, nausea, and weight loss – a picture requiring diagnosis for adrenal insufficiency. Cortisol measurement clarifies the clinical picture where "fatigue" has lasted for months without an obvious cause.

Biomarkers measured