Cortisol is the primary glucocorticoid hormone produced by the adrenal glands and is commonly known as the “stress hormone.” It plays a vital role in regulating metabolism, immune response, blood pressure, and the body’s ability to respond to physical and emotional stress. Cortisol follows a daily rhythm, peaking in the early morning to support alertness and gradually decreasing throughout the day. Measuring total cortisol in blood reflects the combined levels of free and protein-bound cortisol, offering insight into adrenal function and overall hormone balance. Abnormal cortisol levels may be linked to conditions such as adrenal insufficiency, Cushing’s syndrome, chronic stress, or metabolic disorders.