Treatment Approach for Thyroiditis
Initiate beta blockers for symptomatic relief during the thyrotoxic phase, followed by levothyroxine replacement when TSH exceeds 10 mIU/L or when TSH is 4-10 mIU/L with symptoms, while monitoring thyroid function every 4-6 weeks initially. 1, 2
Initial Diagnostic Workup
Before initiating treatment, measure TSH and free T4 as primary diagnostic tests, adding T3 measurement only in highly symptomatic patients with minimal FT4 elevations 1. Obtain TSH receptor antibodies if clinical features suggest Graves' disease (ophthalmopathy, thyroid bruit, or T3 toxicosis) to distinguish from thyroiditis 1, 2. When diagnosis is uncertain, obtain radioactive iodine uptake scan or thyroid ultrasound, as 30-60% of single abnormal TSH values may normalize spontaneously 2.
Thyrotoxic Phase Management
Symptomatic Treatment
- Start beta blockers immediately for palpitations, tremors, and adrenergic symptoms 1, 2
- Monitor thyroid function every 2-3 weeks during this phase 1
- Use nonsteroidal anti-inflammatory drugs or corticosteroids specifically for thyroid pain in subacute thyroiditis 3, 4
When to Escalate Care
Refer to endocrinology if thyrotoxicosis persists beyond 6 weeks 1. For severe symptoms, hospitalize for inpatient management with beta blockers, hydration, supportive care, and consideration of additional therapies under endocrine guidance 1.
Critical Pitfall: Do not use antithyroid medications (methimazole, propylthiouracil) in thyroiditis, as the hyperthyroidism results from release of preformed hormone rather than increased synthesis 3, 4. The FDA label explicitly states levothyroxine is not indicated during the recovery phase of subacute thyroiditis 5.
Hypothyroid Phase Management
Initiation Criteria
Start levothyroxine when:
- TSH >10 mIU/L (regardless of symptoms) 1, 2
- TSH 4-10 mIU/L with symptoms or desire for fertility 2
- Symptomatic hypothyroidism at any TSH level 1
Dosing Strategy
Begin with approximately 1.6 mcg/kg/day based on ideal body weight for patients under 70 years without cardiac disease or frailty 1. Recheck TSH every 4-6 weeks and adjust dose to maintain TSH in normal range 1. Reduce or discontinue levothyroxine if TSH becomes suppressed on therapy 1.
Critical Pitfall: In patients with possible central hypothyroidism (low TSH with low FT4), never start thyroid hormone replacement before administering hydrocortisone, as this can precipitate adrenal crisis 1.
Type-Specific Considerations
Postpartum Thyroiditis
Occurs within one year of delivery, miscarriage, or medical abortion 2, 4. Monitor TSH and FT4 in women who develop goiter or thyroid dysfunction symptoms during this timeframe 1. Approximately 20-30% develop permanent hypothyroidism at one year 2.
Drug-Induced Thyroiditis
Most commonly caused by anti-PD1/PD-L1 immunotherapy 2. Continue immunotherapy in most cases during thyrotoxic phase with conservative management 2. The hypothyroid phase typically leads to permanent hypothyroidism requiring lifelong levothyroxine 2.
Hashimoto Thyroiditis
Presents with elevated thyroid peroxidase antibodies and carries lifelong risk of permanent hypothyroidism 2, 4. Treat with lifelong thyroid hormone therapy when overt hypothyroidism develops 3.
Interferon-Induced Thyroiditis
Occurs in 15-20% of patients receiving peginterferon alpha 6. Discontinue treatment only for severe hyperthyroidism; maintain therapy with careful observation for mild hyperthyroidism 6. For hypothyroidism, continue interferon while administering thyroxine 6. Monitor TSH and free thyroxine at 2-4 month intervals during treatment and regularly for 1 year after termination 6.
Long-Term Monitoring
The natural history of thyroiditis is self-limited, with initial hyperthyroidism typically resolving within weeks and commonly progressing to hypothyroidism 1, 3. Continue surveillance to monitor for permanent hypothyroidism, which occurs in most cases of immunotherapy-induced thyroiditis, 20-30% of postpartum thyroiditis, and nearly all Hashimoto thyroiditis 2.