Hashimoto's Thyroiditis

Aka: Hashimoto's Thyroiditis, Hashimoto's Disease, Hashimoto Thyroiditis, Chronic Lymphocytic Thyroiditis, Chronic Autoimmune Thyroiditis, Askenazy Cell, Hurthle Cell

1. See Also
   1. Hypothyroidism
   2. Thyroiditis
2. Epidemiology
   1. More common in women than men by 3-7 fold
   2. Age of onset peaks at 40-60 years
   3. Increased risk with Family History of autoimmune Thyroid disease
   4. Incidence: 0.3 to 1.5 cases per 1000 persons per year (U.S.)
   5. Prevalence of Antithyroid Antibody
      1. Total population: 3-4%
      2. Euthyroid asymptomatic adolescents: 1.4%
      3. Middle aged to elderly women: 30-40%
3. Pathophysiology
   1. Chronic autoimmune Thyroid inflammation
   2. Thyroid infiltration by Lymphocytes as well as Thyroid fibrosis
   3. Results in formation of Askanazy cells (Hurthle Cells)
4. Risk Factors: Hashimoto's with Hypothyroidism
   1. Excess Iodide intake
   2. Tobacco abuse (thiocyanate exposure)
5. Symptoms
   1. See Hypothyroidism
      1. May initially experience Hyperthyroidism (rarely)
      2. Generalized Fatigue
      3. Weight gain
      4. Cold intolerance
      5. Diffuse myalgias
   2. Painless Thyroiditis (painful in rare cases)
      1. However neck fullness sensation is common
6. Signs
   1. Hypothyroidism
      1. Rarely Thyrotoxicosis occurs due to the Thyroid Autoantibody stimulating effects
   2. ThyroidGoiter (90% of cases)
      1. Symmetric, diffusely enlarged, non-tender Thyroid
      2. Firm, irregular Thyroid surface
      3. Goiter is absent in atrophic form in which fibrosis dominates (with overt Hypothyroidism)
7. Labs
   1. Antithyroid Antibody
      1. Antithyroid Microsomal Antibody (Thyroid Peroxidase Antibody or TPO Antibody)
         1. Present in up to 90-95% of Hashimoto cases (and most specific if significantly elevated)
         2. More mild elevations of TPO Antibody are seen with other thyroid Autoimmunity
            1. Examples: Postpartum Thyroiditis, Silent Thyroiditis, Subacute Thyroiditis
      2. Antithyroglobulin Antibody may be present
      3. TSH-receptor blocking Antibody may be present
   2. Thyroid function stepwise change
      1. First: TSH rises
      2. Next: T4 declines
      3. Next: T3 decline
      4. Last: Symptomatic Hypothyroidism
8. Associated conditions
   1. Pernicious Anemia
   2. Sjogren's Syndrome
   3. Chronic hepatitis
   4. Systemic Lupus Erythematosus
   5. Rheumatoid Arthritis
   6. Adrenal Insufficiency (Addison Disease)
   7. Type I Diabetes Mellitus
   8. Vitiligo
   9. Hepatitis C (untreated)
9. Management
   1. TSH >10 mU/L
      1. Levothyroxine starting at 1.6 mcg/kg/day in all patients
      2. Recheck Serum TSH every 10-12 weeks
   2. TSH 4.5 to 10 mU/L
      1. Pregnancy: Levothyroxine
         1. See Hypothyroidism in Pregnancy for dosing and monitoring frequency
      2. Other: Variable recommendations on whether to treat
         1. Consider treatment for positive TPO Antibody and Hypothyroidism symptoms
         2. If treated
            1. Start Levothyroxine 25 to 50 mcg daily
            2. Recheck Serum TSH in 10-12 weeks
         3. If not treated
            1. Recheck Serum TSH for overt Hypothyroidism in 6-12 months
10. Course
    1. Initially metabolically normal
    2. Later Thyroid failure usually ensues
    3. ThyroidGoiter and symptoms typically resolve by 6 months after becoming euthyroid on replacement
11. Complications: Thyroid Cancers
    1. Primary Thyroid Lymphoma (80 fold increased risk)
       1. Presents as rapidly growing Thyroid Nodule
       2. FNA Thyroid Nodule
    2. Papillary Carcinoma
12. References
    1. Bindra (2006) Am Fam Physician 73:1769-76 [PubMed]
    2. Dayan (1996) N Engl J Med 335:99-107 [PubMed]
    3. Sweeney (2014) Am Fam Physician 90(6): 389-96 [PubMed]