Chronic Fatigue Syndrome Linked to Low T3 Interview with:

Begoña Ruiz Núñez PhD (c) Laboratory Medicine UMC Groningen Co-directora de Healthy Institute President of the Asociación Española de Psico-Neuro-Inmunologí

Begoña Ruiz Núñez

Begoña Ruiz Núñez PhD (c)
Laboratory Medicine UMC Groningen
Co-directora de Healthy Institute
President of the Asociación Española de Psico-Neuro-Inmunologí What is the background for this study?

Response: The diagnosis of Chronic Fatigue Syndrome (​CFS)​ is based on the Fukuda criteria, i.e. symptoms, disability, and exclusion of explanatory illnesses, and not by means of physical signs or abnormalities in laboratory test results​. CFS has been described as a ´allostatic overload condition´, where the physiological mechanisms employed to deal with stress contribute to the perpetuation of the disorder. Chronic Fatigue Syndrome patients are 1.9 times more likely to have a high allostatic load index than healthy controls. Thyroid allostasis-adaptive responses, presenting as ​non-thyroidal-illness syndrome, have been found in many conditions, ranging from critical illness, uremia and starvation to tumor​s​. Taken together, it is possible that, despite TSH and T4 levels within reference ranges, Chronic Fatigue Syndrome symptoms may be attributable in part to allostatic responses, i.e. lower thyroid hormone activity, secondary to chronic (low-grade) inflammation caused by e.g. a compromised gut microbiome and gut wall integrity. What are the main findings? 

Response: The most remarkable observation in this case-control study was that, as a group, the present .Chronic Fatigue Syndrome patients exhibited lower FT3, TT4, TT3, %TT3, SPINA-GD, SPINA-GT, T3/T4 ratios, lower protein binding of thyroid hormones and 24-hour urinary iodine excretion, together with higher %rT3. Sixteen (16%) CFS patients exhibited the ‘low T3 syndrome’ as compared to seven (7%) controls. The ‘low T3 syndrome’ might be in line with recent metabolomic studies pointing at a hypometabolic state in these patients. What should readers take away from your report?

Response: We found that the patients exhibited similar TSH, but FT3 (active thyroid hormone) below the reference range, consistent with the ‘low T3 syndrome’. The latter may fit into their hypometabolic state, that has been compared with a human form of  hibernation.

​The neuroendocrine system consists of a very complex networks, and we just pointed out a small piece of the puzzle. What recommendations do you have for future research as a result of this work?

Response: Our ​study needs confirmation and extension by others. If confirmed, trials with
T3 and iodide supplements, among others, ​ might be indicated.​


Begoña Ruiz-Núñez, Rabab Tarasse, Emar F. Vogelaar, D. A. Janneke Dijck-Brouwer, Frits A. J. Muskiet. Higher Prevalence of “Low T3 Syndrome” in Patients With Chronic Fatigue Syndrome: A Case–Control Study. Frontiers in Endocrinology, 2018; 9 DOI: 3389/fendo.2018.00097

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Last Updated on March 23, 2018 by Marie Benz MD FAAD