Cortisol: Cortisol is a stress hormone produced by the adrenal glands that plays a critical role in the body's stress response and regulation of metabolism, immune function, and energy levels. Dysregulation of cortisol levels can lead to adrenal dysfunction and contribute to symptoms such as fatigue, insomnia, and mood disturbances [16.]. By testing salivary levels of cortisol at 4 time points in a 24 hour period, this test maps out the individual’s diurnal cortisol rhythm and may provide insight into chronic stress, sleep disturbances, immune or digestive dysfunction, and more. [1.]