- Thyroid autoantibodies
- Antithyroid antibodies
- Antithyroglobulin antibody
- Thyroglobulin antibody
- TgAb
- Antimicrosomal antibody
- Antithyroid Peroxidase
- Antithyroid peroxidase antibodies
- Thyroid peroxidase antibodies
- TPO
- TPOAb
- Anti-TPO
- Thyroid microsomal antibody
- 5-7 mL of venous blood
- Red top, tiger top, or gel barrier tube
Additional information
- Handle sample gently to prevent hemolysis
- Send sample to lab immediately
- Thyroid antibodies testing detects the presence and/or measures the titers of autoantibodies to thyroid in the blood
- Several thyroid autoantibodies of immunoglobulin G-type (IgG) are produced in patients with hyperthyroidism, hypothyroidism, and thyroid cancer, such as:
- Thyroglobulin antibody (TgAb)
- Thyroperoxidase antibody (TPOAb)
- Thyroid stimulating hormone receptor immunoglobulins (TSI)
- Sodium-iodide symporter antibody
- TgAb and TPOAb are most common forms used for clinical evaluation
- TgAb are autoantibodies directed against the glycoprotein thyroglobulin located in the thyroid follicles
- TPOAb was initially described as an antimicrosomal autoantibody, that binds with microsomal antigens on cells lining the microsomal membrane located in the cytoplasm of the epithelial cells surrounding the follicles
- The clinical utility of thyroid antibodies (TPOAb and TgAb) include:
- Evaluation of suspected inflammation of the thyroid gland
- Aids in the diagnosis of autoimmune thyroid disease such as Hashimoto’s thyroiditis and Graves disease
- Evaluation of risk in suspected thyroid autoimmunity associated with other autoimmune disorders
- Evaluation of risk of hypothyroidism before initiating drug therapy with lithium, amiodarone, interferon alpha, or interleukin-2 (TPOAb)
- Evaluation of risk of thyroid dysfunction during pregnancy and for post-partum thyroiditis
- Evaluation of risk of miscarriage and in-vitro fertilization failure
- To determine the risk of hypothyroidism in Down syndrome patients
- Detection of autoimmune thyroid disease in patients with nodular goiter, especially in iodide deficient areas (TgAb)
- Evaluate and monitor progression of chronic thyroiditis and thyroid carcinoma (TgAb)
- TgAb should be measured in every serum specimen sent to the laboratory for thyroglobulin (Tg) testing
- Hashimoto thyroiditis is an autoimuune disorder, characterized with hypothyroidism, which is insidious in onset and slowly progresses over months to years. This may clinically present as
- General
- Cold intolerance
- Depression
- Edema (lower extremity)
- Lethargy
- Low energy
- Macroglossia (82%)
- Periorbital or eyelid edema (90%)
- Round puffy face or other facial edema (79%)
- Weight gain
- Neuropsychiatric
- Delayed relaxation of knee and ankle jerk reflex
- Generalized muscle weakness
- Hoarse voice
- Hypokinesia
- Slow speech
- Dermatologic
- Cold, dry, thick scaling skin affecting palms, soles, elbows and knees
- Dry, coarse, brittle hair (76%)
- Dry longitudinally ridged nails
- Loss of axillary, pubic, scalp hair
- Skin may show orange-yellow discoloration
- Cardiovascular
- Bradycardia
- Cardiac enlargement
- Faint cardiac impulse
- Hypertension (diastolic)
- Indistinct heart tones
- Pericardial effusion
- Gastrointestinal
- Ascites
- Constipation
- Menstrual disturbances, impaired fertility
- In severe cases, coma and respiratory failure may occur
- Graves disease is an autoimmune disorder, characterized by hyperthyroidism and may clinically present as:
- Anxious, restless, and fidgeting patient
- Fatigue
- Frequent bowel movements, diarrhea
- Heat intolerance
- Dermatologic
- Finger nails may show onycholysis or brown discoloration
- Hair is fine and silky
- Palmar erythema
- Warm, moist, and velvety
- Neuromuscular
- Fine tremor of fingers, tongue
- Hyperkinesia
- Proximal muscle weakness
- Rapid speech
- Eye changes
- Chemosis
- Infrequent blinking
- Lid lag/Stare
- Periorbital edema
- Proptosis (Exopthalmos)
- Widened palpebral fissures
- Cardiovascular
- Atrial fibrillation
- Cardiac hypertrophy
- Hyperresonant S1 and S2 cardiac sound
- Murmur (systolic)
- Palpitations
- Systolic hypertension
- Tachycardia
- Widened pulse pressure
- Oligomenorrhea or amenorrhea
- High titers of thyroglobulin and thyroid microsomal antibodies (
1:400) strongly suggests Hashimoto thyroiditis, but elevations can also be seen in other autoimmune diseases (given below in high results) - Presence of TPOAb during pregnancy increases the likelihood of post-partum thyroiditis from 10% to 33% as thyroid antibodies can cross the placenta and cause hypothyroidism or hyperthyroidism in the fetus or newborn
- Thyroid antibody profiles in disease/conditions:
Condition/disease TPOAb TgAb Hashimoto thyroiditis 90-100% 80-90% Graves disease 50-80% 50-70% Chronic thyroiditis 70-90% 40-70%
Additional information
- Approximately 10% of women and 3% of men may have low levels of thyroid antibodies with no symptoms of the disease
- The incidence presence of low titers of thyroid antibodies is more common in women and increases with age
- Miscarriage risk is twice as high in women who have antithyroid antibodies
- TgAb is performed along with thyroglobulin (Tg) test, which is used to monitor thyroid cancer, as TgAb interferes with the test results of Tg
- Detection of high titers of TPOAb is more sensitive for the diagnosis of autoimmune thyroiditis than TgAb
- Thyroperoxidase antibody (TPOAb) is an antibody to the main autoantigenic component of microsomes and is a more sensitive and specific test than hemagglutination assays for antimicrosomal antibodies (AMA) in the diagnosis of autoimmune thyroid disease
- Results should be interpreted with caution and serial testing done by the same laboratory using the same methodology because:
- Result vary with different methodologies and laboratory
- May not correlate with the clinical presentations
- Low titer lacks both sensitivity and specificity
- Antibodies are not homogenous
- Factors interfering with test results include:
- Recent radioactive scans or radiation within 1 week before the test (radioimmunoassay method)
- Antibody production may be confined to lymphocytes within the thyroid, resulting in false negative test results
- Related laboratory tests include:
- Complete blood count
- Free thyroxine
- Thyroid biopsy
- Thyroid-stimulating hormone
- Triiodothyronine
Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.
| Conv. Units (IU/mL) | SI Units (kIU/L) | |
|---|---|---|
| TgAb | <14.4 | <14.4 |
| TPOAb | <3.9 | <3.9 |
- TgAb = Antithyroglobulin antibody or Thyroglobulin antibody
- TPOAb = Antiperoxidase antibody or Antimicrosomal antibody
Note that negative (normal) results of both TgAb or TPOAb may be reported by titer (using hemagglutination method) or simply as "Negative" (by Elisa or chemiluminescence).
Conditions associated with elevated levels of thyroid antibodies include:
- Chronic lymphocytic thyroiditis
- Granulomatosis
- Graves disease
- Hashimoto thyroiditis
- Idiopathic myxedema
- Nontoxic nodular goiter (TgAb not increased)
- Pernicious anemia
- Postpartum thyroiditis
- Rheumatoid arthritis (RA)
- Sjogren syndrome
- Subacute thyroiditis
- Systemic lupus erythematosus (SLE)
- Thyroid carcinoma (TgAb not increased in some)
- Drug therapy
- Amiodarone
- Interferon alpha
- Interleukin-2
- Lithium
- ARUP Consult®. Thyroid, Autoimmune. [Homepage on the Internet]©2007. Last reviewed in September 2006. Last accessed on November 14, 2007. Available at URL: http://www.arupconsult.com/Topics/EndocrineDz/ThyroidAutoimmune.html
- ARUP's Laboratories®. Thyroid Antibodies. [Homepage on the Internet]©2007. Last accessed on November 14, 2007. Available at URL: http://www.aruplab.com/guides/ug/tests/0050645.jsp
- Bindra A et al. Thyroiditis. Am Fam Physician. 2006 May 15;73(10):1769-76.
- eMedicine from WebMD®. Graves Disease. [Homepage on the Internet] ©1996-2007. Last updated on July 8, 2005. Last accessed on November 14, 2007. Available at URL: http://www.emedicine.com/med/topic929.htm
- eMedicine from WebMD®. Hashimoto Thyroiditis. [Homepage on the Internet] ©1996-2007. Last updated on May 30, 2006. Last accessed on November 14, 2007. Available at URL: http://www.emedicine.com/med/topic949.htm
- Laboratory Corporation of America. Thyroid Antithyroglobulin Antibody. [Homepage on the internet]©2007. Last updated on October 23, 2006. Last accessed on November 14, 2007. Available at URL: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/se018200.htm
- Laboratory Corporation of America. Thyroid Peroxidase (TPO) Antibodies. [Homepage on the internet]©2007. Last accessed on November 14, 2007. Available at URL: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/ai002400.htm
- LabTestsOnline®. Thyroid Antibodies. [Homepage on the Internet]© 2001-2007. Last reviewed on June 15, 2005. Last accessed on November 14, 2007. Available at URL: http://www.labtestsonline.org/understanding/analytes/thyroid_antibodies/glance.html
- McLachaln SM et al. Why measure thyroglobulin autoantibodies rather than thyroid peroxidase autoantibodies? Thyroid. 2004 Jul;14(7):510-20.