thyroid antibodies

thyroid antibodies

See Antimyeloperoxidase antibody, Antithyroglobulin antibody, Antithyroid peroxidase antibody.

Antibodies, Antithyroglobulin, and Antithyroid Peroxidase

Synonym/acronym: Thyroid antibodies, antithyroid peroxidase antibodies (thyroid peroxidase [TPO] antibodies were previously called thyroid antimicrosomal antibodies).

Common use

To assist in diagnosing hypothyroid and hyperthyroid disease.

Specimen

Serum (1 mL) collected in a red-top tube.

Normal findings

(Method: Immunoassay)
AntibodyConventional Units
Antithyroglobulin antibodyLess than 20 international units/mL
Antiperoxidase antibody
Newborn–3 days0–9 international units/mL
4–30 days0–26 international units/mL
1–12 mo0–13 international units/mL
13 mo–19 yr0–20 international units/mL
20 yr–older adult0–34 international units/mL

Description

Thyroid peroxidase (TPO) is a key enzyme in the formation of thyroid hormones and thyroglobulin is the stored precursor to the active, iodinated thyroid hormones. Antibodies to both may form and affect normal thyroid function. Both tests are normally requested together. Thyroid antibodies are mainly immunoglobulin G–type antibodies. Antithyroid peroxidase antibodies (anti-TPO antibodies) bind with microsomal antigens on cells lining the microsomal membrane of thyroid tissue. They are thought to destroy thyroid tissue as a result of stimulation by lymphocytic killer cells. These antibodies are present in hypothyroid and hyperthyroid conditions. Anti-TPO antibodies are present in Hashimoto’s autoimmune thyroiditis, a major cause of hypothyroidism. Hypothyroidism in women of childbearing age is a significant concern because of the deleterious effects of insufficient thyroxine levels on fetal brain development. Anti-TPO antibodies are also demonstrable in Graves’ disease, a major cause of hyperthyroidism. Graves’ disease is the most common type of thyrotoxicosis in women of childbearing age, impairing fertility and increasing risk of miscarriage to 26%. Transplacental passage of anti-TPO antibodies in pregnant patients may affect the developing fetus or lead to thyroid disease in the neonate. Mild depression is more common in postpartum women with anti-TPO antibodies.

This procedure is contraindicated for

    N/A

Indications

  • Assist in confirming suspected inflammation of thyroid gland
  • Assist in the diagnosis of suspected hypothyroidism caused by thyroid tissue destruction
  • Assist in the diagnosis of suspected thyroid autoimmunity in patients with other autoimmune disorders

Potential diagnosis

Increased in

  • The presence of these antibodies differentiates the autoimmune origin of these disorders from non-autoimmune causes, which may influence treatment decisions.

  • Autoimmune disorders
  • Graves’ disease
  • Goiter
  • Hashimoto’s thyroiditis
  • Idiopathic myxedema
  • Pernicious anemia
  • Thyroid carcinoma

Decreased in

    N/A

Critical findings

    N/A

Interfering factors

  • Lithium may increase thyroid antibody levels.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in evaluating thyroid gland function.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s endocrine and immune systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Note any recent procedures that can interfere with test results.
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include biopsy thyroid, CBC, FT3, FT4, RAIU, T4, thyroid scan, thyroglobulin, TSH, TT3, and US thyroid.
  • See the Endocrine and Immune systems tables at the end of the book for related tests by body system.
References in periodicals archive ?
Thyroid antibodies were negative in the 4 patients for whom a result was available.
Measurements of TSH, FT3 and FT4 were done in all patients, whereas thyroid antibodies (anti-thyroid peroxidase antibodies and anti-thyroglobulin antibodies) could only be done in 118 patients due to cost constraints.
His dose of levothyroxine was adjusted and he was asked to follow up with thyroid antibodies.
The cause of hypothyroidism after RFA of thyroid nodules is unclear, but it is worth noting that two cases of post-RFA hypothyroidism showed increased serum thyroid antibodies (anti-TPOAb and anti-TGAb) before the procedure.
His suggestion was that one should not do thyroid antibodies test, serum calcitonin routinely as their yield is very low.
If one of the thyroid antibodies (anti-Tg, anti-TPO) was positive, this was considered to be a sign of "autoimmunity".
2] It is characterized by the presence of goiter and serum thyroid antibodies.
While thyroid hormones produced by or given to the mother cross the placenta in only limited amounts, both thyroid antibodies and antithyroid drugs (ATDs) readily cross the placenta and affect fetal thyroid function.
These patients were assessed for the presence of thyroid dysfunction, thyroid antibodies and the association with SLEDAI.
It is unusual for a patient with depression and fatigue to be screened with direct thyroid hormone measurements including T4, T3, free T4, free T3, reverse T3, and thyroid antibodies.
Although a causal relationship between OLP and thyroid disease was not investigated in the current study, it can be speculated that circulating thyroid antibodies may trigger an autoimmune response in the oral mucosa and cause development of OLP.
Prospective study of the spontaneous course of subclinical hypothyroidism: prognostic value of thyrotropin, thyroid reserve, and thyroid antibodies.