Long-term Outcome of Subacute Thyroiditis

Abstract

Background Subacute thyroiditis (SAT) is a rare inflammatory disease that presents diagnostic challenges. The underlying pathophysiology and prediction of outcomes are elusive. We investigated the long-term follow-up of SAT for up to 30 years and determined predictors for later hypothyroidism. Methods SAT outcome data from 127 patients (age: 47.6 ± 11.0 yrs., BMI: 24.7±4.8 kg/m²) were analyzed retrospectively. Patients with pre-existing and known causes of hypothyroidism unrelated to SAT were excluded. We also excluded patients without an accelerated erythrocyte sedimentation rate. SAT outcome parameters included anterior neck pain or tenderness of the thyroid, inflammation markers, hypoechoic areas in thyroid ultrasound, hyperthyroidism, fine-needle aspiration, and thyroid scan. Pre-treatment TSH-levels, gender, age, ultrasound findings, anti-thyroid antibodies and markers of inflammation were considered as possible predictors of SAT outcome. Results More than 26.8% of SAT patients developed permanent hypothyroidism within 3 years of treatment. The patient groups later developing hypothyroidism did not differ in age, BMI, pre-treatment TSH levels or initial dosage of prednisolone treatment. However, high cumulative doses of prednisolone were associated with a higher prevalence of hypothyroidism. Also, women were more likely to develop hypothyroidism (OR: 3.18 (95% CI: 1.14–8.65); p=0.0176). Conclusions Our study suggests that one-quarter of patients with SAT develop hypothyroidism in the long-term. Hypothyroidism was predicted by high cumulative doses of prednisolone treatment and female gender. The reported lower prevalence of hypothyroidism in other countries may represent the faster establishment of diagnosis, different treatment protocols, or lower susceptibility to loss of thyroid function. Swift establishment of the diagnosis and rapid tapering of steroids may result in a higher proportion of patients with euthyroidism.

C-reactive protein and thyroid-stimulating hormone levels as risk factors for hypothyroidism in patients with subacute thyroiditis

“…Several studies have shown that a higher proportion of patients who had SAT were females ( 12 , 13 , 19 ). In this study, the female-to-male ratio was 2.18:1, and 62.9% of them were in the 40–60 age range, which confirms the findings of previous studies.…”

“…Many scholars have explored the risk factors for recurrence and hypothyroidism in patients with SAT. The risk of recurrence in patients with SAT was human Page 3 of 20 Accepted Manuscript published as EC-21-0212.R2. Accepted for publication: 21-Jul-2021…”

“…The incidence of hypothyroidism after treatment is 5–27% ( 12 , 13 ), and the incidence of recurrence ranges from 1.6–20% ( 14 , 15 ). Many scholars have explored the risk factors for recurrence and hypothyroidism in patients with SAT.…”

Frequency of Thyroid Antibodies at the Diagnosis of Subacute Thyroiditis

“…Latrofa showed that the Anti-Tg epitope pattern in SAT is different from that in Hashimoto's disease and that the anti-Tg release in SAT disease is transient, with no autoimmune significance (10). It has been hypothesized that patients with autoimmune thyroid disease who have anti-TPO positivity may also develop subacute thyroiditis (8,11) Recently published studies have established that the clinical importance of overlapping of SAT and autoimmune thyroid disease is that autoimmunity has been demonstrated to increase the rate of permanent hypothyroidism after SAT (12)(13)(14)(15)(16). Until recently, an increase in the level of TRAb, just like anti-TPO and anti-Tg, was not expected in patients with SAT.…”

Subakute Thyreoiditis und akute suppurative Thyreoiditis

“…Schließlich entwickelt der Großteil der PatientInnen nach 6-12 Monaten wieder eine normale Schilddrüsenfunktion [13]. Dennoch kann es bei bis zu einem Viertel der Betroffenen zu einer permanenten Hypothyreose kommen, die eine Schilddrüsenhormonsubstitution mit Levothyroxin erfordert [14].…”