thyroid-stimulating immunoglobulins

thy·roid-·stim·u·lat·ing im·mu·no·glob·u·lins (TSI),

in Graves disease, the antibodies to TSH receptors in the thyroid gland. These antibodies are produced by B-lymphocytes and stimulate the receptors, causing hyperthyroidism. Formerly known as LATS (long-acting thyroid stimulator).

thy·roid-stim·u·lat·ing im·mu·no·glob·u·lins

(TSI) (thī'royd-stim'yū-lāt-ing im'yū-nō-glob'yū-linz) In Graves disease, the antibodies to thyroid stimulating hormone receptors in the thyroid gland. These antibodies are produced by B-lymphocytes and stimulate the receptors, causing hyperthyroidism.

Thyroid-Stimulating Immunoglobulins

Synonym/acronym: Thyrotropin receptor antibodies, Thyroid-Stimulating Immunoglobulins, TRAb (TSH receptor antibodies).

Common use

To differentiate between antibodies that stimulate or inhibit thyroid hormone production related to disorders such as Graves’ disease.

Specimen

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

Normal findings

(Method: Animal cell transfection with luciferase marker) Less than 130% of basal activity.

Description

There are two functional types of thyroid receptor immunoglobulins: thyroid-stimulating immunoglobulin (TSI) and thyroid-binding inhibitory immunoglobulin (TBII). TSI reacts with the receptors, activates intracellular enzymes, and promotes epithelial cell activity that operates outside the feedback regulation for thyroid-stimulating hormone (TSH) ; TBII blocks the action of TSH and is believed to cause certain types of hyperthyroidism (see monograph titled “Thyroid-Binding Inhibitory Immunoglobulin”). These antibodies were formerly known as long-acting thyroid stimulators. High levels in pregnancy may have some predictive value for neonatal thyrotoxicosis: A positive result indicates that the antibodies are stimulating (TSI); a negative result indicates that the antibodies are blocking (TBII). TSI testing measures thyroid receptor immunoglobulin levels in the evaluation of thyroid disease.

This procedure is contraindicated for

    N/A

Indications

  • Follow-up to positive TBII assay in differentiating antibody stimulation from neutral or suppressing activity
  • Monitor hyperthyroid patients at risk for relapse or remission

Potential diagnosis

Increased in

  • Graves’ disease (this form of hyperthyroidism has an autoimmune component; the antibodies stimulate release of thyroid hormones outside the feedback loop that regulates TSH levels)

Decreased in

    N/A

Critical findings

    N/A

Interfering factors

  • Lithium may cause false-positive TBII results.

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 assessing 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 system, 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).
  • 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.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • 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 albumin, antibodies antithyroglobulin, biopsy thyroid, copper, PTH, protein, RAIU, thyroglobulin, TBII, thyroid scan, TSH, T4, free T4, T3, free T3, and US thyroid.
  • Refer to the Endocrine System table at the end of the book for related tests by body system.