Response to the letter to the editor: two cases of subacute thyroiditis after different types of SARS-CoV-2 vaccination

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” (¹). 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 (²,³). 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 (²–⁴). 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 (⁵). 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.

• Funding: none.

REFERENCES

• ¹
  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.
• ²
  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.
• ³
  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.
• ⁴
  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.
• ⁵
  Tamagna E, Hershman J, Premachandra BN. Circulating thyroid hormones in a patient with hyperviscosity syndrome. Clin Chim Acta. 1979;93(2):263-8.

Publication Dates

• Publication in this collection
  28 Nov 2022
• Date of issue
  Nov-Dec 2022

History

• Received
  04 Apr 2022
• Accepted
  08 July 2022