Several cases of subacute thyroiditis were noted over the autumn and winter period of 2000-1 in one endocrine referral centre. This study was undertaken to determine if the incidence of subacute thyroiditis was different from the previous year, whether a seasonal clustering had occurred and whether a specific viral pathogen was responsible.
A diagnosis of subacute thyroididits was made if the patient had evidence of transient hyperthyroidism or biphasic thyroid function in association with negative thyroid autoantibodies, and other supportive evidence (no uptake on Tc99 thyroid scanning, raised serum inflammatory markers, pain in the thyroid bed).
In 2000, 10 cases of subacute thyroiditis presented to the endocrine clinic. This represented 12 % of all presenting cases of thyrotoxicosis. This was compared to 1999 in which only 3 cases of subacute thyroiditis presented, representing 3% of all cases of thyrotoxicosis in that year. This difference is statistically significant (P<0.05). Between September and December 2000 a clustering of cases occurred, with 9 cases occurring within this 4 month period. This is contrary to previous reports that subacute thyroiditis tends to occur in summer months. There was no striking geographical association between the cases. Neither were there any significant findings related to occupation of the patients although two were healthcare workers. Only one patient had raised viral titres during the course of the illness due to influenza B virus. It was unclear whether this was a significant contributing factor to her illness, although influenza viruses are believed to have a role in this condition.