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Thyroiditis refers to inflammation of the thyroid gland. There are many etiologies of thyroiditis, including silent or subclinical thyroiditis, transient hyperthyroidism, acute and subacute infectious thyroiditis, and chronic autoimmune thyroiditis (Graves disease and Hashimoto thyroiditis). Thyroid function tests are used to confirm thyroid disease; depending on results, antithyroid antibody tests may be useful to confirm an autoimmune cause of thyroiditis. Antithyroid antibody tests include tests for thyroid peroxidase (TPO) autoantibodies (TPOAb), thyroid-stimulating hormone (TSH) receptor autoantibodies (TRAb), and thyroglobulin (Tg) autoantibodies (TgAb). ,
Quick Answers for Clinicians
Hashimoto thyroiditis is a slowly progressing disease. Symptoms suggestive of Hashimoto thyroiditis include several nonspecific symptoms of hypothyroidism, such as fatigue, constipation, dry skin, bradycardia, and depression. The thyroid gland may be enlarged and firm. Hashimoto thyroiditis should be suspected in patients with elevated thyroid-stimulating hormone (TSH) and low thyroxine (T4) concentrations.
Symptoms suggestive of Graves disease include nonspecific symptoms of hyperthyroidism, including weight loss, heat intolerance, and tachycardia. Signs may include exophthalmos and a diffuse and enlarged thyroid. Thyroid storm, an acute and life-threatening metabolic state, may occur. Graves disease should be suspected in patients with low thyroid-stimulating hormone (TSH) and elevated thyroxine (T4) concentrations.
Autoimmune polyglandular syndrome type 2 refers to the presence of autoimmune thyroid disease with autoimmune adrenal insufficiency and/or type 1 diabetes mellitus. Associated conditions include celiac disease, primary hypogonadism, myasthenia gravis, vitiligo, alopecia, and chronic atrophic gastritis (with or without pernicious anemia).
Thyroid autoantibodies are antibodies produced by the body against the thyroid gland. The thyroid autoantibodies most frequently tested in clinical practice are thyroid peroxidase autoantibodies (TPOAb), thyroglobulin autoantibodies (TgAb), and thyroid-stimulating hormone (TSH) receptor antibodies (TRAb). There are three classes of TRAb, named for their effect on the TSH receptor: stimulating, blocking, and neutral. Hashimoto thyroiditis, an autoimmune disorder that often results in hypothyroidism, is often associated with TPOAb. Graves disease, an autoimmune disorder that typically results in hyperthyroidism, is usually associated with stimulating TRAb (also referred to as thyroid-stimulating immunoglobulin [TSI]). Other thyroid autoantibodies may also cause forms of autoimmune thyroiditis. For example, blocking TRAb may lead to hypothyroidism. Testing for thyroid autoantibodies is therefore useful in identifying the etiology of thyroid disease. However, thyroid autoantibody testing is not necessary or recommended for monitoring treatment response or disease progression. Thyroid autoantibody testing may also be useful in predicting the risk of thyroid disease; for example, women who are known to have high concentrations of TPOAb are at increased risk for developing hypothyroidism during pregnancy. Thyroid autoantibodies may interfere with thyroid hormone immunoassays; for more information, see the ARUP Consult Analytical Considerations in the Evaluation of Thyroid Function topic.
Indications for Testing
Laboratory testing is used to differentiate autoimmune-mediated thyroid disease (eg, Graves disease or Hashimoto thyroiditis) from other etiologies of hyper- or hypothyroidism, as well as to predict the risk of fetal thyroid dysfunction in mothers with a history of Graves disease and to investigate a potential autoimmune etiology of recurrent miscarriage.
Laboratory Testing
Initial Evaluation
Autoantibody testing may be performed after hypothyroidism or hyperthyroidism has been confirmed by TSH and free thyroxine (T4) testing. Hashimoto thyroiditis is the most likely form of autoimmune thyroiditis if the patient has hypothyroidism (elevated TSH and low free T4 concentrations), whereas Graves disease is most likely if the patient has hyperthyroidism (low TSH and elevated free T4 concentrations). For more information on the initial evaluation of suspected autoimmune thyroid disease, see the ARUP Consult Initial Evaluation of Thyroid Function topic.
Autoantibody Tests
Testing for antithyroid antibodies (TPOAb, TRAb, and TgAb) may be helpful for the diagnosis, monitoring, and prognosis of autoimmune thyroid disease when the clinical picture is unclear. This table presents the biological activity and use of tests for these antibodies in autoimmune thyroid disease.
| TPOAb | TRAb | TgAb | |
|---|---|---|---|
| Biology | TPO is a transmembrane protein essential for synthesis of thyroid hormones | TSH-specific receptor controls thyroid function and cell growth | Tg is the precursor to thyroid hormones and is highly immunoreactive |
| Mechanism | Targeted by thyroid microsomal antibody | TRAb targets TSH receptors and competes with TSH for receptor binding TRAb activity is not affected by TSH concentrations | TgAb is directed against Tg |
| Type | Polyclonal antibody (usually IgG1, IgG4) | 3 classes (IgG antibodies)a
| Polyclonal antibody (IgG1 most common) |
| Evidence of tissue damage | None | TSI may cause tissue damage Blocking antibody does not cause tissue damage | None |
| Clinical use | Healthy Populations | ||
| Detectable in a very small percentage | Not typically detected | Detectable in a small percentage | |
| Graves Disease | |||
Present in ~80% of individuals with GD Presence is diagnostic for GD, but TPOAb testing is not usually performed because TRAb is diagnostic and most sensitive Presence may aid in differentiation of GD from factitious thyrotoxicosis, postpartum thyroiditis, or toxic nodular goiter TPOAb testing may be considered to identify autoimmune thyroiditis in patients with thyroid nodules | TRAb or TSI presence is pathognomonic for GD but not usually necessary for diagnosis unless clinical picture is unclear (eg, in euthyroid cases); newer assays (eg, third generation) are more accurate Prognostic marker for relapse after GD treatment Test results aid in the differentiation of GD from factitious thyrotoxicosis, postpartum thyroiditis, or toxic nodular goiter TRAb testing can be used to evaluate for the presence of euthyroid GD ophthalmopathy | Present in 40-70% of individuals with GD TgAb testing provides no additional information over TRAb or TPOAb results; not recommended for the initial evaluation of autoimmune thyroid disease TgAb testing may be useful when TPOAb measurements are negative and a high clinical suspicion exists for autoimmune thyroid disease | |
| Hashimoto Thyroiditis | |||
Present in >90% of individuals with HT Presence is pathognomonic for HT TPOAb testing is not recommended for HT monitoring | Not present in those with HT | Present in 60-80% of individuals with HT Presence of TgAb is diagnostic for HT, but provides no additional information over TPOAb results (TgAb tests are less sensitive and specific than TPOAb) TgAb testing may be useful when TPOAb measurements are negative and a high clinical suspicion exists for autoimmune thyroid disease | |
| Pregnancy | |||
Present in up to 18% of pregnant women Presence during pregnancy predicts risk for postpartum thyroiditis TPOAb testing may be used to evaluate individuals with recurrent miscarriage, with or without infertility issues Follow-up with TPOAb testing is appropriate in pregnant women with TSH >2.5 mU/L | Presence predicts increased risk of thyroid dysfunction in newborns born to mothers with current GD Presence may predict development of fetal or neonatal GD in patients with hypothyroidism who have been treated for GD (radioactive iodine ablation or thyroidectomy before pregnancy) | Present in up to 18% of pregnant women Presence may predict postpartum thyroiditis | |
| Subclinical Hypothyroidism | |||
| Presence may predict progression to overt hypothyroidism | Not present | Presence may predict progression to overt hypothyroidism | |
| Thyroid Cancer | |||
| Not present | Not present | TgAb testing is primarily used to monitor for thyroid cancer recurrence (after ablation or total thyroidectomy) and to investigate potentially unreliable Tg measurements in thyroid carcinoma TgAb may interfere with Tg measurements and should be assessed with each Tg measurement | |
aClassified based on effect on TSH receptor. TRAb tests measure stimulating (TSI), blocking, and neutral autoantibodies. Standalone tests are available for TSI. TRAb and TSI in combination can be useful in unusual cases of hypothyroidism, such as hashitoxicosis. GD, Graves disease; HT, Hashimoto thyroiditis; IgG, immunoglobulin G; LATS, long-acting thyroid-stimulating autoantibodies; TSI, thyroid-stimulating immunoglobulin | |||
ARUP Laboratory Tests
Quantitative Chemiluminescent Immunoassay
Quantitative Electrochemiluminescent Immunoassay (ECLIA)
Semi-Quantitative Chemiluminescent Immunoassay
References
-
27521067
Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid. 2016;26(10):1343-1421.
-
23246686
Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18(6):988-1028.
-
28056690
Alexander EK, Pearce EN, Brent GA, et al. 2017 Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid. 2017;27(3):315-389.
26670972
Burch HB, Cooper DS. Management of Graves disease: a review [published correction appears in JAMA. 2016;315(6):614]. JAMA. 2015;314(23):2544-2554.
24434360
Caturegli P, De Remigis A, Rose NR. Hashimoto thyroiditis: clinical and diagnostic criteria. Autoimmun Rev. 2014;13(4-5):391-397.
20467363
Eckstein A, Esser J, Mann K, et al. Clinical value of TSH receptor antibodies measurement in patients with Graves' orbitopathy. Pediatr Endocrinol Rev. 2010;7(Suppl 2):198-203.
24424182
Menconi F, Marcocci C, Marinò M. Diagnosis and classification of Graves' disease. Autoimmun Rev. 2014;13(4-5):398-402.
25251231
Sweeney LB, Stewart C, Gaitonde DY. Thyroiditis: an integrated approach. Am Fam Physician. 2014;90(6):389-396.