Thyroid Stimulating Immunoglobulin (TSI)
Fasting Required: No

Specimen: Blood

Lab: Quest Diagnostics

Results: 5-7 business days
Note: Result turnaround times are an estimate and are not guaranteed. Our reference lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.

Description: A form of immunoglobulin G (IgG) that can bind to thyrotropin (TSH) receptors on the thyroid gland. TSIs mimic the action of TSH, causing excess secretion of thyroxine and triiodothyronine. The TSI level is abnormally high in persons with hyperthyroidism due to Graves' disease.

Alternative Name(s): Thyroid Receptor Antibody, Thyroid Stimulating Immunoglobulin