Management of Hashimoto's Thyroiditis
Primary Treatment: Levothyroxine for Hypothyroidism
For patients with Hashimoto's thyroiditis who develop hypothyroidism (elevated TSH), levothyroxine replacement therapy is the definitive treatment, with dosing and monitoring guided by TSH levels and clinical response. 1, 2, 3
Initial Assessment and Diagnosis
Confirm the diagnosis of Hashimoto's thyroiditis by measuring anti-thyroid peroxidase (TPO) antibodies, which are positive in the vast majority of cases and indicate autoimmune etiology. 1, 2, 3
Measure both TSH and free T4 to determine thyroid functional status: elevated TSH with low free T4 indicates overt hypothyroidism requiring immediate treatment, while elevated TSH with normal free T4 indicates subclinical hypothyroidism. 1
Before initiating levothyroxine, rule out concurrent adrenal insufficiency, as starting thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis—this is particularly important in patients with autoimmune thyroiditis who have increased risk of concurrent autoimmune adrenal insufficiency (Addison's disease). 4, 1
Treatment Algorithm Based on TSH Levels
For TSH >10 mIU/L (regardless of free T4 or symptoms):
Initiate levothyroxine therapy immediately, as this level carries approximately 5% annual risk of progression to overt hypothyroidism and is associated with cardiovascular dysfunction. 1
For patients <70 years without cardiac disease, start with full replacement dose of approximately 1.6 mcg/kg/day. 1
For patients >70 years or with cardiac disease/multiple comorbidities, start with 25-50 mcg/day and titrate gradually to avoid precipitating cardiac ischemia, arrhythmias, or heart failure. 1
For TSH 4.5-10 mIU/L with normal free T4 (subclinical hypothyroidism):
Consider treatment if the patient has positive anti-TPO antibodies (which predicts 4.3% annual progression risk versus 2.6% in antibody-negative individuals), symptomatic hypothyroidism, or is pregnant/planning pregnancy. 1
If not treating immediately, monitor TSH every 6-12 months for progression. 1
For normal TSH with positive anti-TPO antibodies (euthyroid Hashimoto's):
Do not initiate levothyroxine therapy, as there is insufficient evidence to support prophylactic treatment in euthyroid patients. 5
Monitor TSH every 6-12 months to detect progression to hypothyroidism. 1
Levothyroxine Dosing and Administration
Instruct patients to take levothyroxine as a single daily dose on an empty stomach, one-half to one hour before breakfast with a full glass of water. 6
Advise patients not to take levothyroxine within 4 hours of iron supplements, calcium supplements, or antacids, as these agents decrease absorption. 6
Adjust dose in 12.5-25 mcg increments based on TSH response, using smaller increments (12.5 mcg) for elderly patients or those with cardiac disease. 1
Monitoring Protocol
Recheck TSH and free T4 every 6-8 weeks after initiating therapy or adjusting dose, as this represents the time needed to reach steady state. 1
Target TSH within the reference range of 0.5-4.5 mIU/L with normal free T4 levels. 1
Once adequately treated and stable, monitor TSH every 6-12 months or sooner if symptoms change. 1
Management of Hashitoxicosis (Thyrotoxic Phase)
Some patients with Hashimoto's thyroiditis initially present with thyrotoxicosis due to release of stored thyroid hormones from destroyed follicles—this is a self-limiting process that typically progresses to hypothyroidism. 4, 2, 7
Use non-selective beta-blockers (preferably with alpha receptor-blocking capacity) for symptomatic relief of palpitations, tremors, anxiety, and heat intolerance during the thyrotoxic phase. 4, 8
Do NOT use antithyroid medications (methimazole or propylthiouracil), as this is destructive thyroiditis, not Graves' disease—the thyroid is not overproducing hormone. 4
Monitor TSH every 2-3 weeks during the thyrotoxic phase to detect transition to hypothyroidism, which typically occurs within 1-2 months. 4, 8
Initiate levothyroxine therapy when TSH becomes elevated, as the thyrotoxic phase leads to permanent hypothyroidism in most cases. 4
Special Populations and Considerations
Pregnant women or those planning pregnancy:
Treat any degree of TSH elevation before conception, as subclinical hypothyroidism during pregnancy is associated with preeclampsia, low birth weight, and potential neurodevelopmental effects in offspring. 1
Target TSH <2.5 mIU/L before conception and during pregnancy. 1
Levothyroxine requirements typically increase by 25-50% during pregnancy, necessitating dose adjustment and more frequent monitoring (TSH every trimester). 1
Patients with cardiac disease:
Start with 25-50 mcg/day and increase slowly by 12.5 mcg increments every 6-8 weeks, as rapid normalization can unmask or worsen cardiac ischemia. 1
Monitor for new or worsening angina, palpitations, dyspnea, or arrhythmias at each follow-up. 1
Patients on immune checkpoint inhibitors:
Thyroid dysfunction occurs in 6-20% of patients receiving PD-1/PD-L1 or CTLA-4 inhibitors, with Hashimoto's-like thyroiditis being common. 4
Consider treatment even for subclinical hypothyroidism if fatigue or other hypothyroid symptoms are present. 1
Continue immunotherapy in most cases, as thyroid dysfunction rarely requires treatment interruption. 4, 1
Associated Autoimmune Conditions
Screen for other autoimmune disorders, as 20-30% of patients with Hashimoto's thyroiditis have concurrent autoimmune conditions. 3, 9
Check vitamin B12 levels periodically, as autoimmune thyroid disease patients are at increased risk for pernicious anemia. 1
Screen for adrenal insufficiency in patients with unexplained hypotension, hyponatremia, hyperpigmentation, or hypoglycemia that cannot be fully explained by hypothyroidism alone. 1
Monitor for development of other organ-specific autoimmune disorders including type 1 diabetes, celiac disease, and vitiligo. 9
Critical Pitfalls to Avoid
Never start levothyroxine before ruling out adrenal insufficiency in patients with suspected central hypothyroidism or multiple autoimmune conditions, as this can precipitate adrenal crisis. 4, 1
Do not treat based on a single elevated TSH value—confirm with repeat testing after 3-6 weeks, as 30-60% of elevated TSH levels normalize spontaneously. 1
Avoid overtreatment, which occurs in 14-21% of treated patients and increases risk for atrial fibrillation, osteoporosis, fractures, and cardiac complications—approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH. 1, 6
Do not assume hypothyroidism is permanent without reassessment—some patients have transient thyroiditis that resolves, particularly in the recovery phase from Hashitoxicosis. 1
Recognize that many symptoms in euthyroid Hashimoto's patients (normal TSH) may not be attributable to thyroid dysfunction and may represent associated autoimmune or neuropsychological conditions that require separate evaluation. 5
Thyroid Cancer Surveillance
Patients with Hashimoto's thyroiditis have a 1.6 times higher risk of papillary thyroid cancer and 60 times higher risk of thyroid lymphoma compared to the general population. 2