Objective.To evaluate diagnostic features of subacute thyroiditis (ST) in patients unvaccinated against COVID-19.

Materials and methods. The study included 26 female patients with ST aged 24 to 46 years without a medical history of thyroid disorder before ST development, with regular menstrual cycle (1st group — non-COVID-19 reconvalescent patients; 2nd group — COVID-19 reconvalescent patients treated with glucocorticoids (GCs.) in complex therapy;
group 3 — COVID-19 reconvalescent patients that did not use GCs. in COVID 19 therapy). In all the patients complete blood count was made, thyroid-stimulating hormone, free thyroxine (T4fr.), antibodies to thyroid peroxidase, C-reactive protein (CRP) and ferritin were evaluated. Ultrasound examination of the thyroid gland and thyroid scintigraphy with 99mTc-pertehnetate were carried out with the calculation of radiotracer uptake index.

Results. As a result of the study, COVID-19 reconvalescent patients were found out to have mild microcytic anemia, higher ferritin and CRP values at the time of PT manifestation. In the group receiving GCs, еrythrocyte’s sedimentation rate and lymphocyte values were lower compared to the group of patients without COVID-19, and group 3 patients; also, the group receiving GCs. had the smallest values of the uptake index according to the results of thyroid scintigraphy and reliably large values of the T4fr level. COVID-19 reconvalescent patients require more potent ST therapy: in group
2 100% patients required an increase in GCs dose, in group 3 in 87.5% cases GCs were added to non-steroidal anti-inflammatory drug and in groups 2 and 3 there was an increase in the duration of therapy to 51 and 44 days, compared with 25 days of treatment in group 1.

Conclusions. The study revealed that the groups of female patients who were COVID-19 reconvalescent patients had certain characteristic features in diagnosis, therapeutic approach and ST outcomes.