Higher Prevalence of "Low T3 Syndrome" in Patients With Chronic Fatigue Syndrome: A Case-Control Study

Begona Ruiz-Nunez*, Rabab Tarasse, Emar F. Vogelaar, D. A. Janneke Dijck-Brouwer, Frits A. J. Muskiet

*Corresponding author for this work

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    Abstract

    Chronic fatigue syndrome (CFS) is a heterogeneous disease with unknown cause(s). CFS symptoms resemble a hypothyroid state, possibly secondary to chronic (low-grade) (metabolic) inflammation. We studied 98 CFS patients (21-69 years, 21 males) and 99 age- and sex-matched controls (19-65 years, 23 males). We measured parameters of thyroid function, (metabolic) inflammation, gut wall integrity and nutrients influencing thyroid function and/or inflammation. Most remarkably, CFS patients exhibited similar thyrotropin, but lower free triiodothyronine (FT3) (difference of medians 0.1%), total thyroxine (TT4) (11.9%), total triiodothyronine (TT3) (12.5%), % TT3 (4.7%), sum activity of deiodinases (14.4%), secretory capacity of the thyroid gland (14.9%), 24-h urinary iodine (27.6%), and higher % reverse T3 (rT3) (13.3%). FT3 below the reference range, consistent with the "low T3 syndrome," was found in 16/98 CFS patients vs. 7/99 controls (OR 2.56; 95% confidence interval = 1.00-6.54). Most observations persisted in two sensitivity analyses with more stringent cutoff values for body mass index, high-sensitive C-reactive protein (hsCRP), and WBC. We found possible evidence of (chronic) low-grade metabolic inflammation (ferritin and HDL-C). FT3, TT3, TT4, and rT3 correlated positively with hsCRP in CFS patients and all subjects. TT3 and TT4 were positively related to hsCRP in controls. Low circulating T3 and the apparent shift from T3 to rT3 may reflect more severely depressed tissue T3 levels. The present findings might be in line with recent metabolomic studies pointing at a hypometabolic state. They resemble a mild form of "non-thyroidal illness syndrome" and " low T3 syndrome" experienced by a subgroup of hypothyroid patients receiving T4 monotherapy. Our study needs confirmation and extension by others. If confirmed, trials with, e.g., T3 and iodide supplements might be indicated.

    Original languageEnglish
    Article number97
    Number of pages13
    JournalFrontiers in endocrinology
    Volume9
    DOIs
    Publication statusPublished - 20-Mar-2018

    Keywords

    • chronic fatigue syndrome
    • thyroid
    • "low T3 syndrome"
    • triiodothyronine
    • reverse triiodothyronine
    • urinary iodine
    • inflammation
    • high-sensitive C-reactive protein
    • NONTHYROIDAL ILLNESS SYNDROME
    • CHRONIC INFLAMMATORY DISEASES
    • EUTHYROID SICK SYNDROME
    • THYROID-HORMONE
    • SYNDROME ME/CFS
    • CYTOKINE PRODUCTION
    • METABOLIC FEATURES
    • MONONUCLEAR-CELLS
    • ALLOSTATIC LOAD
    • IMMUNE FUNCTION

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