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Why We Measure Cortisol Levels

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It is often assumed that stress causes an increase in your main stress hormone – cortisol.  Cortisol, you will recall, is the major player in your body’s fight-or-flight response to stress. 

The association between stress and the hypothalamic-pituitary-adrenal (HPA) axis has been extensively investigated ever since the pioneering work of Hans Selye in 1936.  Specifically, stress-induced elevations in cortisol, the principle hormone produced by the HPA axis and the main player in your fight-or-flight stress response have been well documented.  Think of your HPA axis as a well-orchestrated interconnected set of biological systems designed to manage physical, mental, and emotional challenges.  It is particularly sensitive to situations that involve new or uncontrollable situations, physical danger, and social threat. This elaborate and ancient (or else we as a species would not have survived thus far) mechanism is known as your adaptive stress response.  It is designed to be activated literally in the blink of an eye when confronted with danger to prepare you to fight or to flee.  It likewise is designed to last only moments and then return to baseline (homeostasis).   

Sustained activation, on the other hand, of your body’s adaptive stress response as a result of repeated stress over time leads to persistently elevated cortisol levels causing the all too well known “wear and tear” (allostatic load) symptoms of chronic stress.  Essential to the definition of allostasis is this notion of a rapid recovery to optimal functioning following a threat or stressor.

The majority of research attention to the classic fight-or-flight stress response has focused on over-activation of this stress system and high cortisol.  Moreover, many if not most patients and clinicians alike believe that stress-induced elevations in cortisol cause our most common stress-related disorders. Theory and data, however, clearly indicate that under-activation (low-cortisol) is also an important contributor to many common health conditions. Indeed, at least as early as 1998, definitions of chronic stress and allostatic load have included both over- and under-activation of the HPA axis.  And although high-cortisol has received the bulk of the research and clinical attention, we now know that both too much and too little cortisol contribute to modern diseases. 

For example, over the past decade, numerous researchers have found an association between low baseline cortisol levels (and sluggish cortisol reactions to normal stress) in persons suffering from post-traumatic stress disorder (PTSD), fibromyalgia, and chronic fatigue syndrome. 

More recently, researchers at the Psychiatric Neuroscience Laboratory at the Australian Institute of Tropical Health and Medicine (AITHM) at James Cook University (JCU) have shown that individuals with psychosis produce low amounts of cortisol after they wake up in the morning (Cortisol Awakening Response, CAR).  Results of the study are published in Neuroscience & Biobehavioral Reviews and indicate that low CAR levels may represent a safe and easy to measure biomarker that can be used to identify people at risk for schizophrenia early. 

JCU Associate Professor Zoltan Sarnyai concluded that measuring cortisol levels could become a valuable technique to identify those who will develop full-blown psychosis from amongst those who present with early stages of the disease.

The paper, a meta-analysis of 11 clinical studies, also highlighted evidence to suggest that high-risk individuals who later develop psychosis already have changes in cortisol before they develop the illness.  Furthermore, according to Dr. Sarnyai, low CAR levels have also been associated with systemic inflammation and changes in the gut microbiome, meaning that measurement of cortisol levels might provide the potential for earlier diagnosis and, thereby, earlier treatment of these conditions as well. 


Clinical symptoms alone are seldom sufficient to guide treatment recommendations – meds, lifestyle, vitamins, supplements, or some combination.  Although I have gotten better at correlating your symptoms to specific biological imbalances (after 30 plus years in practice you would certainly hope so), in the absence of measuring cortisol levels, it is still just an educated and experienced guess.  It is for that and other reasons that I so often order a NeuroAdrenal Profile on my patients and clients. 

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