Cortisol and allostatic load: the wear of being switched on

Cortisol gets a bad name. It gets blamed for weight that gathers around the middle, for wrecked sleep, for the wired but tired feeling that so many professionals and parents describe in clinic. The truth is less dramatic and more useful: cortisol itself is not the problem. It is a hormone your body needs every day, to get you out of bed, to manage blood sugar and inflammation, and to meet anything unexpected. The problem is a stress response that switches on appropriately and then never quite switches off.

What allostasis actually means

Physiologists have a word for the healthy version of this system: allostasis, the process of maintaining stability through change. Your nervous system and hormones are constantly adjusting, heart rate, blood pressure, cortisol, blood sugar, to whatever the moment asks of you, a stressful meeting, a broken night with a sick child, a run for the tram. That adjusting is not a flaw. It is the system doing exactly its job.

The trouble starts when the demands stack up faster than the body can recover from them, or when a demand that should be short lived gets treated as constant. Neuroscientist Bruce McEwen, who did much of the foundational work in this area, called the cumulative cost of that adjusting allostatic load, the wear and tear that builds up on the body and brain when the stress response is activated too often, for too long, or is never given the chance to reset between demands.^[1] An earlier paper he wrote with Eliot Stellar put it plainly: the same systems that protect us in the short term can, over time, damage us if they never get that chance to settle.^[2]

The rhythm cortisol is meant to follow

Left alone, cortisol has a clear daily pattern. It rises sharply in the thirty to forty five minutes after you wake, giving you the alertness to get up and get moving, then falls gradually across the day and reaches its lowest point in the first hours of sleep, before the cycle begins again. That morning rise and steady decline is coordinated by the hypothalamic pituitary adrenal axis, the command chain that links the brain to the adrenal glands and governs how the whole stress system behaves under load.^[3]

A body under sustained load tends to lose that clean rhythm. The pattern can flatten, arrive earlier than it should, or refuse to settle in the evening, which is one reason a stressed nervous system so often shows up as a mind that will not switch off at bedtime. We look at this in more detail in why a stressed nervous system tends to wake you at 3am.

What the wear actually looks like

Allostatic load is not an abstract idea. In clinic it shows up as a fairly recognisable list, and most people arrive already carrying several items on it without having connected them to each other:

• Sleep that will not deepen, even when there is enough time for it, or a mind that switches on the moment the lights go off.
• Digestion that has become unpredictable, a gut that is more reactive than it used to be.
• Muscles, especially through the neck, jaw and lower back, that stay braced even at rest, guarding against a threat that is not actually there.
• A fog through the middle of the day, trouble finding words, a memory that used to be sharper.

Dr Arthur Kaganovitch (Chiropractor), who founded Aura in Toorak, describes this as a body stuck in the protection phase long after the thing that put it there has passed. None of it means a person is falling apart. It means the nervous system has been asked to hold a brace for too long, and the body is telling on itself in the areas that were already carrying the most.

Why a blood test at one moment says so little

It is a reasonable instinct to want a number. The trouble with a single cortisol blood test, taken at one moment on one day, is that cortisol is meant to vary hugely across a normal twenty four hours by design. A high reading at 9am might be an entirely normal morning peak. A low reading at 4pm might be an entirely normal afternoon low. One snapshot cannot tell a rhythm working properly from a rhythm that has come apart, because it was never built to capture a rhythm at all.

What matters is not what your cortisol was at nine o’clock on a Tuesday. It is how your whole system is coping, day after day, and whether it ever gets the chance to stand down.

How we measure the load instead

Rather than chasing a single number, an assessment at Aura looks at how your nervous system is functioning as a whole, and it does that against your own baseline rather than a population average. Heart rate variability gives a read on how well the balance between your stress response and your recovery response is working moment to moment.^[4] We explain what that measurement actually captures in heart rate variability, explained. Thermography maps the skin temperature pattern either side of the spine, which reflects how evenly the nervous system is regulating that area. A hands-on examination adds the third piece, finding where the body is holding tension it should not need to hold. Together they build a picture of load that a single blood draw cannot, and one we can track and compare over time. You can read more about how we think about the nervous system generally on our nervous system page.

This matters particularly for anyone dealing with recurring headaches, which are one of the more common places sustained load shows up first. If that is you, our headaches page sets out how we approach it.

Where to start

If any of this sounds familiar, chasing symptoms one at a time tends to be less useful than understanding the load sitting underneath them. The starting point is a first visit, which begins with a $99 Initial Assessment, ordinarily $189. It is for new patients only, one per person, and there is no obligation to continue.