thyroid-stimulating immunoglobulins
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p880
2025-09-15
406
thyroid-stimulating immunoglobulins (TSIs, Long-acting thyroid stimulator [LATS], Thyroid-binding inhibitory immunoglobulin [TBII], Thyrotropin receptor antibody, Thyroid-stimulating hormone receptor [TSHR] antibodies)
Type of test Blood
Normal findings
TSI: < 130% of basal activity
TBII: < 10% inhibition
Test explanation and related physiology
TSIs represent a group of immunoglobulin G (IgG) anti bodies directed against the thyroid cell receptor for TSH and are associated with autoimmune thyroid disease states, such as chronic thyroiditis and Graves disease. (These autoantibodies bind and transactivate the TSHRs). This instigates stimulation of the thyroid gland independent of the normal feedback-regulated TSH stimulation. This, in turn, will stimulate the release of thy roid hormones from the thyroid cells. Some patients with Graves disease also have TSHR-blocking antibodies, which do not transactivate the TSHR. The balance between TSI and TSHR blocking antibodies, as well as their individual titers, is thought to be a determinant of Graves disease severity.
The use of these antibodies is helpful in the evaluation of patients for whom the diagnosis of Graves disease is confused by conflicting data (e.g., subclinical Graves hyperthyroidism.
Because TSIs can cross the placenta, they may be found in neonates whose mothers have Graves disease.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: red or gold
• Notify the laboratory if the patient has received radioactive iodine in the preceding 2 days.
• Handle the blood sample gently. Hemolysis may interfere with interpretation of test results.
Abnormal findings
Increased levels
- Hyperthyroidism
- Malignant exophthalmos
- Graves disease
- Hashimoto thyroiditis
- Neonatal thyrotoxicosis
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