Treatment of Subacute Thyroiditis

Initial Assessment and Monitoring

Obtain baseline TSH, free T4, and inflammatory markers at presentation 1
Monitor thyroid function every 2-3 weeks during the initial phase to detect the transition from hyperthyroidism to hypothyroidism 1, 2
T3 measurement can be helpful in highly symptomatic patients with minimal FT4 elevations 1

The American College of Cardiology recommends beta-blocker therapy (propranolol or atenolol) for symptomatic hyperthyroidism, including palpitations, tremors, anxiety, and fever 1, 2
Continue immune checkpoint inhibitor therapy if applicable, as thyroiditis rarely requires treatment interruption 3, 4
Provide hydration and supportive care 1
If thyrotoxicosis persists beyond 6 weeks, refer to endocrinology for additional workup to rule out Graves' disease 1, 2

Treat hypothyroidism with levothyroxine replacement when TSH is elevated with low FT4, or when TSH >10 mIU/L even with normal FT4 3, 2
For patients <70 years without cardiac disease or frailty, start full replacement at approximately 1.6 mcg/kg/day based on ideal body weight 1
For patients >70 years or with cardiac comorbidities, start with 25-50 mcg daily 1
In asymptomatic patients with elevated TSH but normal FT4 during recovery, consider monitoring for 3-4 weeks before treating to assess for spontaneous recovery 1
If TSH becomes low on therapy, reduce or discontinue levothyroxine as this suggests overtreatment or recovery of thyroid function 1

Missing the transition from hyperthyroidism to hypothyroidism due to inadequate monitoring can lead to delayed treatment 2
Continuing levothyroxine when thyroid function recovers can lead to iatrogenic hyperthyroidism 1
Failing to recognize that subacute thyroiditis is self-limited, with hyperthyroidism typically resolving within weeks, can lead to unnecessary treatment 1