Total Serum Cortisol Test

A total serum cortisol test measures the level of this glucocorticoid steroid hormone in the blood. It is produced and secreted by the adrenal cortex under the control of the hypothalamic-pituitary-adrenal (HPA) axis. Cortisol plays a central role in the body's stress response, regulating metabolism (glucose, protein, and fat), regulating blood pressure, and suppressing the immune response. Its secretion follows a daily pattern (circadian rhythm), peaking in the early morning and reaching its lowest point around midnight.