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What is Euthyroid Sick Syndrome?

By Lucy Rose Clinic

January 14, 2021

Euthyroid Sick Syndrome or Low T3 syndrome is often a missed issue because it is not a standard thyroid assessment test.

And it usually has nothing to do with your thyroid gland….

Today let’s have a look at this issue, what it presents like, and what we can do about it.

Signs and Symptoms of Euthyroid Sick Syndrome

Are you struggling with any of these?

  • Persistent fatigue.
  • Sensitive to cold weather, or feeling cold all the time.
  • Difficulty losing weight, or gaining weight easily.
  • Thinning hair, and noticeable hair loss.
  • Low blood pressure, and heart palpitations.
  • Slower than normal pulse rate.
  • Mood swings.
  • Depression.
  • Brain fog.
  • Poor memory and concentration.
  • Swelling around the throat.
  • Muscle and joint pain.
  • For women, menstrual problems, or irregular periods.
  • Dry Skin
  • Sluggish digestion, and constipation.
  • Face, hands and feet are swollen and puffy.
  • Low libido

Then read on!

Standard hypothyroidism involves high levels of thyroid stimulating hormone (TSH) and low levels of the thyroid hormones T4 and T3. Symptoms are very classic, with fatigue, weight gain, and hair shedding being the top three complaints – but there are over 20 symptoms you can have when you have this type of hypothyroidism.

Low T3 syndrome is where the TSH is sitting normal, the T4 is normal, but the T3 is low.

And considering that T3 is the ACTIVE form of thyroid, this is significant.

If you have ever had your thyroid tested and it was said to be fine, then this could relate to you. The only way to find out for sure is with a thorough thyroid test, as well as checking the status of other vital body systems that work with the thyroid hormones.

Low T3 Syndrome

Medically, this is also called Euthyroid Sick Syndrome (ESS), Non-thyroidal Illness Syndrome (NTIS), and Low T3 Syndrome.

The main difference between Low T3 Syndrome and classic hypothyroidism is that it is NOT an issue with the thyroid gland.

Causes of Euthyroid Sick Syndrome

Most studies have been done on people in extreme circumstances, such as admittance to ER – Emergency Room, and people dealing with life threatening illness.

But luckily there is more interest in understanding the role of T3 in the arena of wellness and preventative health, and also in chronic disease.


Often T4 and T3 are tested, rather than free T4 and free T3. While total T4 and T3 give us important information about what the thyroid gland itself is producing, free T4 and T3 tell us how much thyroid hormone is actually available at the cellular level to exert its metabolic effects.

Of importance, reverse T3 must also be tested as a part of the picture, and other tests may be needed depending on your situation.

Inflammation – the Root Of All Illness

Inflammation can be caused by an infection, autoimmune disease, obesity, diabetes or another chronic illness. Just about any disease you can think of is characterised by inflammation, so if you are living with chronic disease, your hormones are affected.

Interleukin-6 (IL-6) is positively correlated with reverse T3 and negatively correlated with free T3. The more IL-6 that is circulating in your blood, the less active thyroid hormone you’ll have available to your cells and tissues.

Other studies have shown that lipopolysaccharide (LPS), a bacterial endotoxin, can downregulate TSH, T4 and T3 levels.

The HPT Axis

The hypothalamic-pituitary-thyroid (HPT) axis regulates the production of endocrine hormones, including TSH, T4 and T3. When T3 is low, is can be due to an issue with this feedback loop. Inflammation and either a decline in serum leptin levels, or leptin resistance, are two major causes.


Fasting or diminished calorie intake can lead to decreased T3 levels, and this is thought to be mediated by a decrease in circulating leptin.


Hashimoto’s patients have a higher than normal prevalence of also having an autoimmune issue affecting the pituitary gland. The pituitary gland is responsible for regulating hormones which affect growth, sexual development, metabolism and human reproduction.


Enzymes responsible for activation of thyroid hormone in the liver, kidney, skeletal muscles and other peripheral tissues are called deoidinases. There are 3 types – D1, D2 and D3, and their job is to convert T4 to T3. 


Diet is the most powerful friend or foe in your health. This is even more important if you have a thyroid problem.

Understanding exactly what is driving your symptoms is the key to empowerment on the healing path, and helps you to understand why you may need to eat in a certain way.

At the very least, adopting a diet that support less inflammation is a good start – no processed foods, no sugar, no additives. Lots of fresh organic fruit, vege and clean protein sources, and lots of filtered water.

We really help people get their health sorted faster when they run food intolerance testing to accurately remove foods from the diet that are causing inflammation.

As we mentioned earlier, inflammation is the bane of all health issues, so taking control by reducing drivers of inflammation as much as is feasibly possible is important. This includes stress, sleep, personal purpose, and self talk as well – as they can all trigger a stress response in the body when out of balance.


One interesting study was done with 22 women, aged 30 to 40, with medicated hypothyroidism completed a six-month yoga practice. Each session lasted one hour, and sessions were held four times per week.

At the end of the study, the participants had significantly reduced total cholesterol, LDL cholesterol, and triglycerides, and increased HDL cholesterol levels. Although TSH levels were not significantly different from baseline, they trended downwards, and seven of the 22 women were able to reduce their hormone medication dosage.

This shows the influence of mindfulness, conscious breathing, and movement on the body.

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“I would highly recommend … the Lucy Rose Clinic for anyone who is wanting answers and help with their health. I have struggled with constant exhaustion and gut issues for some time now and it got to the point that I just started to think that they were just ‘normal’ for my body. Well I was wrong! I have never felt so good since diagnosing and starting treatment for my gut and thyroid along with multiple deficiencies and intolerance’s I never knew I had!” – J.T.

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If you are ready to get your thyroid properly assessed, book your first call now.

Book a consult and talk to one of our naturopaths 🙂


Effect of 6 months intense Yoga practice on lipid profile, thyroxine medication and serum TSH level in women suffering from hypothyroidism: A pilot study – PubMed (


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