How Chronic Stress Impacts Thyroid Function

Your adrenal glands are better known for producing adrenaline and cortisol (see DUTCH TEST) and managing your fight or flight response. However, did you know that, as part of your endocrine system, they also produce hormones that impact major metabolic processes, just like your thyroid does?

The hormones produced by your adrenal glands help to regulate blood pressure, electrolyte balance, blood sugar, immune response, digestion, and more.

When you experience stress, whether it is emotional, mental, or physical, your hypothalamus sends a signal to your pituitary gland. Your pituitary gland signals your adrenal glands to produce and release a series of stress hormones, including cortisol. This is the Hypothalamus Pituitary Axis or HPA axis. You may hear me talk about this on social media and refer to it as like an ‘air traffic controller and the subordinate’ (hypothalamus and pituitary), signalling to the pilot (gland) because it can sense how many planes are in the air (hormones).

Once a stressor triggers this cascade of hormones, cortisol and your other stress hormones redirect your body’s normal functions to essentially ignore anything that is not necessary for overcoming the stressor in front of you. This means that functions such as digestion, immune response, and yes, thyroid hormone production and distribution, are temporarily put on hold or slowed down until the stress has passed. Ideally, the stress passes quickly, your body returns to normal, and everything runs smoothly once more.

Unfortunately, due to our hectic lifestyles, many of us experience chronic stress, either because our stress does not end quickly or it is quickly followed by another stressor. This state of chronic stress puts your adrenals on overdrive for extended periods of time, continuously flooding your body with cortisol until your adrenals can no longer keep up with the constant demand for more and more stress hormones, leaving you in a state of ‘adrenal fatigue’. This flooding and eventual plummeting of stress hormones have many negative impacts on the thyroid.

Reduced Thyroid Hormone Production

Cortisol functions in a negative feedback loop with the hypothalamus and pituitary gland. Once it enters your bloodstream, its presence signals your hypothalamus and pituitary gland to slow down so that they don’t trigger any additional stress hormones. These glands also regulate thyroid hormone production, so that slows down as well (HPT axis).

Reduced T4 to T3 Conversion

Stress hormones affect the enzymes that convert T4 to  T3.  Free T3 (FT3) is the active form of the hormone that is the one that actually does the work and helps you lose weight, stops your hair thinning or you feeling cold and boosts your energy. Reverse T3 (RT3) is the inactive form of the hormone. When stress is high the conversion of T4 to T3 is slowed down and we can also convert more of our T3 into RT3 rather than FT3. This imbalance essentially puts the brakes on all of your metabolic processes, slowing them down and causing hypothyroid symptoms.

Thyroid Hormone Resistance

Also released in the stress response are inflammatory immune cells called cytokines, which make thyroid receptors less sensitive to thyroid hormones. This means that even if you’re taking thyroid medication and your thyroid hormone levels are normal, you can still be suffering from underactive thyroid symptoms. This is something we often see in clinic and why the inflammatory marker, CRP is tested for in our at-home thyroid test. In clinic we often find that clients on thyroid medication but still experiencing symptoms achieve great relief by following our advice on anti-inflammatory diet and supplements.

Oestrogen Dominance and Thyroid Hormone

Prolonged cortisol elevation can cause excess oestrogen to accumulate (Oestrogen Dominance). This extra oestrogen increases levels of thyroid-binding globulin (TBG), which is the protein that allows your thyroid hormones to travel through your bloodstream. When thyroid hormones are attached to TBG they remain inactive, so T4 can’t be stored in your tissues or converted to Free T3.

How to Best Test Adrenal function

As mentioned above, your adrenal function plays a huge role in the effectiveness of your thyroid hormones. It is very important to determine if adrenal stress is an underlying cause of your thyroid dysfunction. That way you can treat them side by side.

In fact, many of our clients with adrenal-related thyroid problems who are put on thyroid medication by their doctor without adrenal support can initially get worse. They can experience a racing heart or shaking hands as their body is forced into overdrive from the sudden rush of thyroid hormones.

Conventional doctors typically rely on a one-off morning blood test to measure cortisol levels, but your stress hormone levels fluctuate significantly throughout the day. That means the one-time test does not provide nuanced results. If you want to test your cortisol levels at home, I recommend using our Dutch CAR (available from our practitioners) or any of our Dutch Hormone tests available here, which include the CAR.

With a full assessment and test results (where possible), we can advise on the right dietary and lifestyle changes and supplements (including glandulars that work in a similar way to thyroid medication).