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Hashimoto's thyroiditis
Background
Overview
Definition
HT, also known as chronic lymphocytic thyroiditis and autoimmune thyroiditis, is a chronic autoimmune disorder characterized by inflammation of the thyroid gland, leading to its gradual destruction and hypothyroidism.
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Pathophysiology
The pathophysiology of HT involves progressiveimmune-mediated destruction of the thyroid gland, driven by genetic susceptibility and environmental factors. Infiltration by T and B lymphocytes and the production of anti-TPO and anti-thyroglobulin antibodies contribute to follicular damage and impaired hormone synthesis, ultimately leading to hypothyroidism. Histologic findings include parenchymal atrophy, lymphoid follicles with germinal centers, fibrosis, and Hurthle cell metaplasia.
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Epidemiology
HT is the most common cause of hypothyroidism in iodine-sufficient regions. The annual incidence is estimated at 0.3-1.5 cases per 1,000 individuals. Global adult prevalence is approximately 7.5%, with rates of 17.5% in women and 6.0% in men. It predominantly affects women, with a female-to-male ratio of 10:1, and is most commonly diagnosed between ages 30-50.
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Risk factors
Risk factors include female sex, advancing age, personal or family history of autoimmune disease, genetic predisposition involving HLA-DR and CTLA-4 polymorphisms, high iodine intake, exposure to radiation, an d certain medications (such as interferon-alpha, amiodarone) and medical treatments (such as radioactive iodine therapy for hyperthyroidism, external beam radiation therapy for head and neck malignancies, and thyroid surgery). Some infections and environmental stressors may also contribute.
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Disease course
HT is a chronic and progressive condition, with many patients remaining asymptomatic and euthyroid for years before developing overt hypothyroidism. Some experience phases of subclinical hypothyroidism. Progression to hypothyroidism is more likely in patients with high antibody titers or TSH elevation at presentation. When symptoms occur, they are usually related to hypothyroidism and include fatigue, weight gain, cold intolerance, constipation, bradycardia, dry skin, and depression. A painless, diffusely enlarged thyroid (goiter) may be present. In some cases, transient hyperthyroidism may occur due to follicular rupture and hormone release. Related risks and complications include infertility, miscarriage, myxedema, hyperlipidemia, and cardiovascular risk due to untreated hypothyroidism. There is a small increased risk of thyroid lymphoma. Goitrous enlargement may cause compressive symptoms in rare cases.
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Prognosis and risk of recurrence
With appropriate treatment, prognosis is excellent. Most patients on levothyroxine remain euthyroid and symptomatically well. However, long-term monitoring is needed, as dosage adjustments may be required over time due to progression or other factors such as weight changes or pregnancy.
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Guidelines
Key sources
The following summarized guidelines for the evaluation and management of Hashimoto's thyroiditis are prepared by our editorial team based on guidelines from the American Diabetes Association (ADA 2025), the European Academy of Dermatology and Venereology (EADV 2021), the Endocrine Society (ES 2020), the British Medical Journal (BMJ 2019), the American Thyroid Association (ATA 2017), the American College of Endocrinology (ACE/AACE ...
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Screening and diagnosis
Indications for screening: as per ADA 2025 guidelines, obtain screening for autoimmune thyroid disease in patients with T1DM soon after diagnosis and periodically thereafter if clinically indicated.
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Indications for testing (dyslipidemia)
Indications for testing (dermatitis herpetiformis)
Indications for testing (infertility)
Indications for testing (poor lactation)
Diagnostic investigations
Anti-TPO antibodies: as per AACE/ATA 2012 guidelines, measure anti-TPO antibodies in the evaluation of patients with subclinical hypothyroidism.
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Thyroid hormone tests
Medical management
Thyroid replacement therapy, indications, abnormal TSH: as per BMJ 2019 guidelines, do not initiate thyroid replacement therapy in adult patients with subclinical hypothyroidism.
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Thyroid replacement therapy (indications, normal TSH)
Thyroid replacement therapy (choice of agent and dosing)
Thyroid replacement therapy (treatment targets)
Management of thyroid nodules
Management of dyslipidemia
Nonpharmacologic interventions
Iodine supplementation, general population: as per AACE/ATA 2012 guidelines, do not use iodine supplementation, including kelp or other iodine-containing functional foods, in the management of hypothyroidism in iodine-sufficient areas.
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Iodine supplementation (during pregnancy)
Iodine supplementation (during breastfeeding)
Selenium supplementation
Specific circumstances
Pregnant patients, screening: as per ATA 2017 guidelines, obtain verbal screening for any history of thyroid dysfunction and prior or current use of either thyroid hormone or antithyroid medications in all pregnant patients at the initial prenatal visit.
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Pregnant patients (evaluation)
Pregnant patients (management of autoantibodies)
Pregnant patients (management of normal TSH levels)
Pregnant patients (thyroid replacement therapy)
Pregnant patients (treatment targets)
Pregnant patients (monitoring)
Pregnant patients (postpartum)
Breastfeeding patients
Patients with infertility
Patients with combined adrenal insufficiency
Patient education
General counseling
As per ATA 2017 guidelines:
Advise patients receiving levothyroxine therapy to independently increase their dose of levothyroxine by 20-30% (such as taking 2 additional tablets weekly of the current daily levothyroxine dosage) and urgently notify their caregiver for prompt testing and further evaluation in case of a suspected or confirmed pregnancy (positive home pregnancy test).
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Counsel treated hypothyroid female patients of reproductive age regarding the likelihood of increased demand for levothyroxine during pregnancy. Advise such patients to contact their caregiver immediately upon a confirmed or suspected pregnancy.
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Follow-up and surveillance
Indications for specialist referral: as per AACE/ATA 2012 guidelines, manage most patients with primary hypothyroidism by non-endocrinologist physicians familiar with the diagnosis and treatment of hypothyroidism. Refer patients with hypothyroidism meeting any of the following criteria for a consultation with an endocrinologist:
infant and pediatric patients
female patient planning conception
pregnant patients
patients difficult to render and maintain in a euthyroid state
cardiac disease
presence of goiter, nodule, or other structural changes in the thyroid gland
presence of other endocrine diseases, such as adrenal or pituitary disorders
unusual constellation of thyroid function test results
unusual causes of hypothyroidism, such as induced by agents interfering with the absorption of levothyroxine, impacting thyroid gland hormone production or secretion, affecting the hypothalamic-pituitary-thyroid axis (directly or indirectly), increasing clearance, or peripherally impacting metabolism.
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Laboratory follow-up