The globulin formerly known as long-acting thyroid stimulator (LATS) is one of the biologically unique autoantibodies with the effect of stimulating the target cell. Now called thyroid-stimulating immunoglobulins (TSI, TSIg), these antibodies react with the cell surface receptor that usually combines with TSH. The TSI reacts with the receptors, activates intracellular enzymes, and promotes epithelial cell activity that operates outside the feedback regulation for TSH.

• TSI is not normally detected in the serum, although it may be found in the serum of about 5 percent of people without apparent hyperthyroidism or exophthalmos.

• Administration of radioactive iodine preparations within 24 hours of the test may alter results.

• Known or suspected thyrotoxicosis with elevated levels found in 50 to 80 percent of affected individuals
• Determination of possible etiology of exophthalmos as indicated by elevated levels
• Monitoring of response to treatment for thyrotoxicosis with possible relapse indicated by elevated levels

Nursing Care Before the Procedure

Client preparation is essentially the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

• The client should not have received any radioactive iodine preparations within 24 hours of the test.

A venipuncture is performed and the sample collected in a red-topped tube. The sample should be handled gently to avoid hemolysis and transported promptly to the laboratory.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.