Management of Thyroiditis

Initial Assessment and Diagnosis

The American College of Endocrinology recommends measuring TSH and free T4 to determine the phase of thyroid dysfunction, followed by targeted symptom management with beta blockers for thyrotoxic symptoms and monitoring for progression to hypothyroidism 1, 2
Most patients with thyroiditis present with asymptomatic (painless) thyroiditis showing high free T4 or T3 levels with low/normal TSH 1, 2
The thyrotoxic phase occurs an average of one month after immunotherapy initiation in drug-induced cases 1
Thyrotoxicosis may present with weight loss, palpitations, heat intolerance, tremors, anxiety, diarrhea, and hypermetabolic symptoms, though these may be masked by beta blockers 1, 2
Fatigue can be a presenting symptom even in the thyrotoxic phase, despite seeming counterintuitive 3

Measure thyroid stimulating hormone receptor antibody (TRAb) or thyroid stimulating immunoglobulin (TSI) to rule out Graves' disease 1, 2
Check thyroid peroxidase (TPO) antibody levels, particularly for Hashimoto thyroiditis 1
Consider radioactive iodine uptake scan (RAIUS) or Technetium-99m pertechnetate thyroid scan if recent iodinated contrast was not used 1, 2
Thyroiditis is the most frequent cause of thyrotoxicosis with immune checkpoint inhibitors, occurring more commonly with anti-PD1/PD-L1 drugs than anti-CTLA-4 agents 1
Graves' disease is very rare and occurs more commonly with anti-CTLA-4 drugs 1, 2

Thyroiditis is a self-limiting process requiring only symptomatic treatment 1, 2
Prescribe non-selective beta blockers, preferably with alpha receptor-blocking capacity, for symptomatic patients with palpitations, tremors, or anxiety 1, 2

Repeat thyroid hormone levels (TSH and free T4) every 2-3 weeks during the thyrotoxic phase 1, 2
The thyrotoxic phase typically lasts approximately one month 1, 2
Hypothyroidism develops an average of 1 month after the thyrotoxic phase and 2 months from immunotherapy initiation 1, 2
Unexplained fatigue, weight gain, hair loss, cold intolerance, constipation, and depression indicate progression to hypothyroidism 1
Lab tests showing high TSH and low free T4 confirm biochemical hypothyroidism 1

Start levothyroxine at the time of hypothyroidism diagnosis, with full replacement dose of approximately 1.6 mcg/kg/day for patients <70 years without cardiac disease 4
For patients >70 years or with cardiac disease/multiple comorbidities, start with lower dose of 25-50 mcg/day and titrate gradually 4
Thyroiditis leads to permanent hypothyroidism in most cases, requiring lifelong thyroid hormone replacement 1, 2
Before initiating levothyroxine, rule out concurrent adrenal insufficiency, as starting thyroid hormone before corticosteroids can precipitate adrenal crisis 1, 4

Endocrinology consultation is recommended in all cases of suspected or confirmed thyroiditis, to ensure appropriate management of the evolving thyroid dysfunction 1, 2
Specialist input is particularly important for drug-induced thyroiditis in patients on immunotherapy 1
Continue immune checkpoint inhibitor therapy in most cases, as thyroid dysfunction rarely requires treatment interruption 4