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20 March 2018 - MedicalXpress - Chronic fatigue syndrome possibly explained by lower levels of key thyroid hormones

Frontiers

chronic fatigue syndrome

New research demonstrates a link between chronic fatigue syndrome (CFS) symptoms and lower thyroid hormone levels. Published in Frontiers in Endocrinology, the study indicates that CFS, a condition with unknown causes, can be explained by lower thyroid hormones - but may be distinct from thyroidal disease. This finding can be seen as a first step to finding treatment for a debilitating illness for which there is no recognized treatment.

FAB RESEARCH COMMENT:

In this study, people with chronic fatigue syndrome (CFS) showed low levels of both active thyroid hormone (T3), and the inactive or 'storage' form (T4), together with elevated levels of 'reverse T3' - an abnormal form of thyoid hormone that 'competes' with T3 by blocking receptors without activating them.  

Importantly, CFS patients also showed normal levels of another hormone - thyroid stimulating hormone (TSH), which is supposed to rise when T3 and/or T4 levels fall too low, stimulating the thyroid to produce more.*

The study also found increased low-grade inflammation, and lower urinary iodine levels, in the CFS patients compared with controls. An adequate supply of iodine is crucial to healthy thyroid function (T3 contains 3 molecules of iodine, while T4 contains 4). However, dietary iodine intake was not assessed - and many people's diets are relatively lacking in iodine, as fish and seafood or dairy products are the main dietary sources. See
As the researchers emphasise - these new findings do NOT yet offer any new treatment options for Chronic Fatigue Syndrome (and like most 'diagnoses' in psychiatry, this is a broad and purely descriptive label, not an explanatory one).

They do, however, provide objective evidence of anomalies in thyroid function that are consistent with some of the core symptoms of CFS, and deserve further investigation that could help develop treatments for this debilitating and relatively common condition.  

* Elevated TSH remains the standard test for diagnosing underactive thyroid (hypothyroidism). However, there is good evidence that the TSH test alone is NOT a reliable measure of thyroid hormone levels or activity, so a reliance on this single measure can leave many people with serious but untreated symptoms from an underactive thyroid. 

For more information on this issue, see Hoermann et al 2018, - and for non-specialists, a very simplified summary of this research article can be found on the 'News & Media' page (4/1/18) at Thyroid UK - who have long campaigned for better assessment and management of thyroid problems.

See the underpinning research here:

See also:

New research demonstrates a link between chronic fatigue syndrome (CFS) symptoms and lower thyroid hormone levels. Published in Frontiers in Endocrinology, the study indicates that CFS, a condition with unknown causes, can be explained by lower thyroid hormones—but may be distinct from thyroidal disease. This finding can be seen as a first step to finding treatment for a debilitating illness for which there is no recognized treatment.

Chronic fatigue syndrome is a common disease marked by lengthy spells of weakness, fatigue and depression. Its diagnosis is predominantly based on symptoms and on ruling out any underlying medical condition, rather than on laboratory tests and physical examination.

Interestingly, several symptoms resemble those of hypothyroidism—a condition where the thyroid gland does not produce enough thyroid hormone. In hypothyroidism, the body tries to encourage thyroid hormone activity by releasing more thyroid-stimulating hormone—however, this does not happen in patients with chronic fatigue syndrome.

This contrast in thyroid-stimulating activity led the study's authors to hypothesize that chronic fatigue syndrome is caused by low activity of thyroid hormones in the absence of thyroidal disease.

Led by Dr. Begoña Ruiz-Núñez at the University Medical Center Groningen, The Netherlands, the researchers compared thyroid function and markers of inflammation between 98 CFS patients and 99 healthy controls. Remarkably, the CFS patients had lower serum levels of certain key thyroid hormones such as triiodothyronine (T3) and thyroxine (T4), but normal levels of thyroid-stimulating hormone.

Additional analyses indicated that CFS patients had a lower urinary iodine status and low-grade inflammation, which possibly mirrored the symptoms of patients with hypothyroidism. These CFS patients, however, had relatively higher levels of another thyroid hormone called "reverse T3" or rT3. This appeared to be due to a shift in hormone production, where the body preferred to convert T4 to rT3 instead of producing T3. The low T3 levels found in CFS patients coupled with this switchover to rT3 could mean that T3 levels are severely reduced in tissue.

"One of the key elements of our study is that our observations persisted in the face of two sensitivity analyses to check the strength of the association between CFS and thyroid parameters and low-grade inflammation," says Dr. Ruiz-Núñez. "This strengthens our test results considerably."

The researchers believe inclusion of patient information, such as duration of illness, would enable a correlation with their biochemical profiles. Further, even though the study demonstrates a link between chronic fatigue syndrome symptoms and low levels of key thyroid hormones, a definitive cause for CFS remains unknown.

If the study findings are confirmed by additional research, it may pave the way for a treatment for chronic fatigue syndrome.