Test Catalog

Test ID: TSI    
Thyroid-Stimulating Immunoglobulin, Serum

Method Description Describes how the test is performed and provides a method-specific reference

This bioassay compares the cyclic adenosine monophosphate (cAMP) production of thyroid-stimulating hormone (TSH)-responsive cells upon exposure to patient serum with that obtained in the same cells after exposure to normal control serum.


The assay uses Chinese hamster ovary cells that have been permanently transfected with the human thyroid-stimulating hormone receptor (TSHR) and a luciferase expression construct under the control of a cAMP responsive promoter. Luciferase transcription in these cells is proportional to the concentration of intracellular cAMP.


The cells are grown to near-confluence. An aliquot of cells is then incubated with each diluted patient serum. Cells are lysed at the end of incubation, luciferase substrate is added and chemiluminescence is measured in a luminometer. The ratio of the light-units produced in the cell-lysate exposed to patient serum divided by a control cell-lysate light-signal is the TSI index.(Preissner CM, Wolhuter PJ, Sistrunk JW, et al: Comparison of thyrotropin-receptor antibodies measured by four commercially available methods with a bioassay that uses Fisher-rat thyroid cells. Clin Chem 2003;49:1402-1404; package insert: Thyroid Stimulating Immunoglobulin Assay. Diagnostic Hybrids)

PDF Report Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 6 days

Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

3 months

Performing Laboratory Location Indicates the location of the laboratory that performs the test