Sitting above each kidney are two small endocrine glands about the size of walnuts. These are the adrenal glands, responsible for producing hormones that help control some of the body’s most critical functions. Among these hormones, cortisol is particularly critical for survival. Often referred to as the “stress hormone,” it helps the body adapt to a wide range of challenges—both emotional and physical, such as trauma or infection—by regulating overall metabolism. Despite its central role in stress and endocrine biology, how the adrenal gland is built and how it functions remains poorly understood.

About one in three employees in Singapore report feeling burnt out—one of the highest rates globally. Burnout and chronic fatigue carry a substantial economic cost and pose serious risks in professions where alertness is critical. Yet diagnosing fatigue and related mental health conditions today relies largely on self-reported questionnaires, which tend to be subjective, intermittent, and poorly suited to real-time evaluation.