DEAR EDITORS AND COLLEAGUES,
We would like to thank Mungmunpuntipantip and Wiwanitkit for their comments and contributions to our article “Two cases of subacute thyroiditis after different types of SARS-CoV-2 vaccination” (11 Bostan H, Ozturk Unsal I, Kizilgul M, Gul U, Sencar ME, Ucan B, et al. Two cases of subacute thyroiditis after different types of SARS-CoV-2 vaccination. Arch Endocrinol Metab. 2022;66(1):97-103.). They commented on the possible mechanisms of vaccine-associated subacute thyroiditis (SAT) and emphasized that subclinical thyroid disorders in the pre-vaccine period should be excluded. We do agree that the exclusion of subclinical thyroid problems is a factor that strengthens the possible relationship. We would like to emphasize that these patients were euthyroid in their routine follow-up visits before the vaccination. In our article, we mentioned that both cases did not have any known thyroid or autoimmune disorder before the coronavirus disease 2019 (COVID-19) vaccination. However, recently, cases of SAT, Graves' disease (GD) relapses, and even conversion from Hashimoto's disease to GD have been reported after the COVID-19 vaccination (22 Oğuz SH, Şendur SN, Iremli BG, Gürlek A, Erbas T, Ünlütürk U. SARS-CoV-2 vaccine-induced thyroiditis: Safety of Re-vaccinations and Clinical Follow-up. J Clin Endocrinol Metab. 2022;dgac049.,33 Bostan H, Ucan B, Kizilgul M, Calapkulu M, Hepsen S, Gul U, et al. Relapsed and newly diagnosed Graves’ disease due to immunization against COVID-19: A case series and review of the literature. J Autoimmun. 2022;128:102809.). This raises the question that vaccination may be a triggering factor for relapse in patients with pre-existing autoimmune/inflammatory thyroid disorders.
Immunological mechanisms, such as molecular mimicry, epitope spreading, bystander activation, and adjuvant effect, have been postulated in COVID-19 vaccine-associated thyroid disorders (22 Oğuz SH, Şendur SN, Iremli BG, Gürlek A, Erbas T, Ünlütürk U. SARS-CoV-2 vaccine-induced thyroiditis: Safety of Re-vaccinations and Clinical Follow-up. J Clin Endocrinol Metab. 2022;dgac049.–44 Jafarzadeh A, Nemati M, Jafarzadeh S, Nozari P, Mortazavi SMJ. Thyroid dysfunction following vaccination with COVID-19 vaccines: a basic review of the preliminary evidence. J Endocrinol Invest 2022:1-29.). Mungmunpuntipantip and Wiwanitkit speculated that post-vaccine hyperviscosity may be another mechanism that causes abnormal thyroid hormone levels. However, both the absence of a symptom suggesting hyperviscosity in our cases and the recurrent thyroid diseases reported after vaccination against COVID-19, highlights possible immunological mechanisms. In addition, previously, Tamagna and cols. stated that increased T4 levels in a patient with hyperviscosity syndrome may be due to the interference of increased protein concentrations (55 Tamagna E, Hershman J, Premachandra BN. Circulating thyroid hormones in a patient with hyperviscosity syndrome. Clin Chim Acta. 1979;93(2):263-8.). In conclusion, although hyperviscosity may explain some thromboembolic events associated with COVID-19 and its vaccination, we believe that further evidence is needed to link it with autoimmune/inflammatory thyroid diseases.
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Funding: none.
REFERENCES
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1Bostan H, Ozturk Unsal I, Kizilgul M, Gul U, Sencar ME, Ucan B, et al. Two cases of subacute thyroiditis after different types of SARS-CoV-2 vaccination. Arch Endocrinol Metab. 2022;66(1):97-103.
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2Oğuz SH, Şendur SN, Iremli BG, Gürlek A, Erbas T, Ünlütürk U. SARS-CoV-2 vaccine-induced thyroiditis: Safety of Re-vaccinations and Clinical Follow-up. J Clin Endocrinol Metab. 2022;dgac049.
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3Bostan H, Ucan B, Kizilgul M, Calapkulu M, Hepsen S, Gul U, et al. Relapsed and newly diagnosed Graves’ disease due to immunization against COVID-19: A case series and review of the literature. J Autoimmun. 2022;128:102809.
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4Jafarzadeh A, Nemati M, Jafarzadeh S, Nozari P, Mortazavi SMJ. Thyroid dysfunction following vaccination with COVID-19 vaccines: a basic review of the preliminary evidence. J Endocrinol Invest 2022:1-29.
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5Tamagna E, Hershman J, Premachandra BN. Circulating thyroid hormones in a patient with hyperviscosity syndrome. Clin Chim Acta. 1979;93(2):263-8.
Publication Dates
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Publication in this collection
28 Nov 2022 -
Date of issue
Nov-Dec 2022
History
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Received
04 Apr 2022 -
Accepted
08 July 2022