For this first installment I have pulled together a variety of research articles.
Krysiak R, Szkróbka W, Okopień B. The Effect of Gluten-Free Diet on Thyroid Autoimmunity in Drug-Naïve Women with Hashimoto's Thyroiditis: A Pilot Study. Exp Clin Endocrinol Diabetes. 2019;127(7):417-422. doi:10.1055/a-0653-7108
I read this article in 2019 when it came out and was excited to see that research is starting to support what we have known clinically for years. Many patients with Hashimoto’s Thyroiditis (HT) benefit from a gluten free diet. The sample size was small and it wasn’t randomized, patients were allowed to choose the gluten free group or the control group. That said, even with the small sample size there was an improvement in both TPO and TG antibodies in the gluten free group as well as a slight increase in thyroid hormone output.
The authors hypothesize that the improvement in autoimmunity may be due in part to an increase in vitamin D that was seen in the gluten free group. The participants did not increase their vitamin D intake and it’s unknown why a gluten free diet would have improved their vitamin D status.
This study is very interesting and I hope it’s the first of many exploring the important connection between a gluten free diet and HT.
Vitamin D and Hashimoto’s (2016 + 2018)
Sahin, M., Corapcioglu, D. The effect of vitamin D on thyroid autoimmunity in non-lactating women with postpartum thyroiditis. Eur J Clin Nutr 70, 864 (2016). https://doi.org/10.1038/ejcn.2016.56
Xu J, Zhu XY, Sun H, et al. Low vitamin D levels are associated with cognitive impairment in patients with Hashimoto thyroiditis. BMC Endocr Disord. 2018;18(1):87. Published 2018 Nov 26. doi:10.1186/s12902-018-0314-7
We know from observational studies that low vitamin D status seems to contribute to thyroid autoimmunity. What sets this research apart is that they looked at women post partum to see what impact vitamin D supplementation has on antibodies. If you are familiar with Hashimoto's you probably know post partum is a common time for the condition to flare.
The investigators found that the women with post partum thyroiditis (PPT) had lower levels of vitamin D than post partum women without thyroiditis. Giving vitamin D (either 2,000IU or 4,000IU depending on the patient's vitamin D blood level) to the PPT women significantly lowered their antibodies without any side effects. Between 20-40% of women with PPT go on to develop permanent hypothyroidism and lowering antibodies is an important step to prevent that outcome.
The second study looks at the relationship between vitamin D, Hashimoto's Thyroiditis (HT), and cognitive impairment.
We already know that low vitamin D is correlated with cognitive impairment in the general population and that there is a high prevalence of low vitamin D in patients with HT. It wasn't surprising that they found low vitamin D is associated with cognitive impairment in patients with HT.
The authors also found that vitamin D levels were inversely related to TPO antibody levels.
Bottom line study #1 and #2: If you have Hashimoto's I highly recommend talking to your provider about your vitamin D level.
Depression and Hashimoto’s (2011 + 2014)
Giynas Ayhan M, Uguz F, Askin R, Gonen MS. The prevalence of depression and anxiety disorders in patients with euthyroid Hashimoto's thyroiditis: a comparative study. Gen Hosp Psychiatry. 2014;36(1):95-98. doi:10.1016/j.genhosppsych.2013.10.002
Hardoy MC, Cadeddu M, Serra A, et al. A pattern of cerebral perfusion anomalies between major depressive disorder and Hashimoto thyroiditis. BMC Psychiatry. 2011;11:148. Published 2011 Sep 13. doi:10.1186/1471-244X-11-148
The first study looked at the prevalence of depression and anxiety in euthyroid Hashimoto’s thyroiditis. Euthyroid Hashimotos’ is when a patient has Hashimoto’s but their thyroid hormones are not abnormal (yet!). They looked at patients who have a normal FT3, FT4 and TSH but also have thyroid antibodies and an abnormal thyroid ultrasound. There are already several studies that show a higher prevalence of psychiatric disorders in patients with Hashimoto’s but this study is unique in that they only included HT patients who had ‘normal’ thyroid function based on thyroid hormone testing. Surprise! They found there was a higher prevalence of anxiety and depression in these patients than in the general population or control. There are many theories as to why HT patients have a higher incidence of psychiatric disorders and many center around imbalanced levels of TSH, FT3 and FT4. There is likely more to the story. This study might be the first to find a relationship between OCD and HT. The prevalence of OCD in the HT group was 15.7% and the prevalence in the general population is around 0.8% to 3.2%.
Bottom line study #1 - If you have anxiety or depression and your thyroid has been screened with just a TSH make sure to talk to your provider about a comprehensive screen that includes antibody or ultrasound testing especially if you have a family history of thyroid disorders.
The authors summarized the second study very well so I am going to quote the authors directly “The debate on the pathogenesis of depression in thyroid autoimmunity involves two hypothesis, it is suggested that the neuronal tissue is hypersensitive to hormonal deficiencies and are more vulnerable to possible subclinical hormonal deficiencies not detectable with routine laboratory tests. In the second hypothesis, a possible pathogenic factor linked to inflammation is postulated, consequent to cytokine activation or extraglandular lesions similar to vasculitis induced effects.”
In other words it could be that our brains are hypersensitive to fluctuations in thyroid hormone so even when the levels are ‘normal’ our brains might suffer and/or there is likely a role of inflammation in altering blood flow.
Bottom line study #2: Depression and brain blood flow changes happen with HT (both euthyroid and hypothyroid) and patients with depression, especially atypical depression, need comprehensive thyroid screening.
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