Thyroid dysfunction and Microflora: Is there a connection?

Dr. J. asked me to look at any relationship of microflora (gut bacteria) with hypothyroidism and hyperthyroidism. Since hypothyroidism is associated with Chronic Fatigue Syndrome, I suspect there is — the question is whether anyone has studied it and published any papers on it. As usual, I restrict myself to PubMed source. – many of the studies were not human based… we take what we can find…

  • Diet appears to impact thryroid size.[2010 Study], with a connection to Phytase and it’s role with the availability of phosphorus in the body.
  • ” it should never be forgotten that gut communities contain important metabolic niches inhabited by species with highly specific metabolic capability.” with certain metabolites being supplied by only one or two species..[2008 Study]
  • “Thyroid hormones can therefore have vitamin-like effects and, in conjunction with vitamin D, and possibly with other steroids, may be more aptly termed vitamones” [1997 Study]
  • “The phytosterol-containing treatments induced the increased activity of thyroid glands, as evident by elevated levels of serum total thyroxine, total triiodothyronine, and free triiodothyronine.” [2013 Study]
  • Helicobacter pylori decreases the ability to absorb thyroid hormones [2011 Study]
  • Gram Negative bacteria produces lipopolysaccharides which regulates thyroid and pituitary functions [2010 Study]
  •  Streptococcus pneumoniae infection reduces thyroid levels[2009 Study]
  • Enterobacteriaceae (Yersinia enterocolitica) has been implicated with increased risk
  •  Enterococcus faecium (probiotic) modulates “the activation of genes selected for functional interaction between the hypothalamic-pituitary-thyroid(HPT) axis and the melanocortin and the endocannabinoid systems [2011 Study]

So the answer is, some thyroid dysfunction is associated with gut bacteria, especially with the ability to absorb thyroid hormones. We know that H Pylori should be tested for, and eliminated if found. We do not know the good and bad bacterias.  There seems to be more information on raising thyroid levels (by diet, eliminating H. Pylori) then in reducing it. For high levels, diet changes could help — but the path is not clear.

Postscript: During this research I came across some interesting articles on antinutritional factors which I suspect are relevant to Chronic Fatigue Syndrome.

  • “high levels of dietary trypsin inhibitors from soybeans, kidney beans, or other grain legumes can cause substantial reductions in protein and amino acid digestibilities… , the presence of high levels of tannins in cereals, such as sorghum, and grain legumes, such as fababean (Vicia faba L.), can result in significantly reduced protein and amino acid digestibilities”[*][2012 Study]