From the Guidelines
Thyroid-stimulating immunoglobulin (TSI) testing should be used in the management of Graves' disease to confirm diagnosis, monitor treatment effectiveness, and predict the likelihood of remission, with the goal of minimizing morbidity, mortality, and improving quality of life. When managing Graves' disease, TSI testing is crucial as it helps in diagnosing the condition by identifying the presence of autoantibodies that stimulate the thyroid gland to produce excess thyroid hormones. During treatment with antithyroid medications, periodic TSI measurements can help predict the likelihood of remission, with declining TSI levels suggesting a higher chance of remission, and persistently elevated levels indicating a higher risk of relapse after medication discontinuation 1. Key points to consider in the management of Graves' disease using TSI include:
- Measuring TSI levels at diagnosis to confirm the presence of Graves' disease
- Using antithyroid medications such as methimazole or propylthiouracil to manage the condition, with the goal of maintaining FT4 or FTI in the high-normal range using the lowest possible thioamide dosage
- Monitoring TSI levels periodically during treatment to predict the likelihood of remission
- Considering definitive treatment options like radioactive iodine ablation or thyroidectomy in patients with persistently elevated TSI levels or those who are at high risk of relapse
- Being aware of the potential side effects of thioamide therapy, including agranulocytosis, hepatitis, vasculitis, and thrombocytopenia, and discontinuing the medication if these symptoms develop 1. In pregnant women with Graves' disease, TSI monitoring is particularly useful as these antibodies can cross the placenta and affect the fetus, potentially causing neonatal hyperthyroidism. The biological basis for TSI testing is that these antibodies mimic TSH by binding to TSH receptors on thyroid cells, stimulating excessive thyroid hormone production, which is the fundamental pathophysiology of Graves' disease. By using TSI testing in the management of Graves' disease, clinicians can make informed decisions about treatment and minimize the risks associated with the condition, ultimately improving patient outcomes and quality of life.
From the Research
Use of TSI in Management of Graves' Disease
- TSI (Thyroid Stimulating Immunoglobulin) is a useful tool in the diagnosis and management of Graves' disease, as it measures the functional activity of TSH-receptor antibodies 2.
- TSI levels are significantly higher in patients with Graves' disease compared to normal controls, and there is a strong correlation between TSI and TRAb (TSH-receptor antibodies) in these patients 2.
- After treatment with anti-hyperthyroidism medication, TSI and TRAb levels significantly decrease, and patients who are still positive for TSI or TRAb antibodies at 5 years of follow-up are at a higher risk of relapse 2.
- The higher the TSI level at initial diagnosis, the longer the duration of treatment with anti-hyperthyroid drugs and the higher the risk of relapse 2.
- Early changes in TSI bioassay over anti-thyroid drug treatment can predict prognosis of Graves' disease, with a less decremental TSI bioassay response to treatment associated with a higher risk of relapse or persistence 3.
Clinical Applications of TSI
- TSI can be used to monitor the response to treatment and predict the risk of relapse in patients with Graves' disease 2, 3.
- TSI bioassay can help identify patients who are likely to achieve remission after anti-thyroid drug treatment, and those who may require longer-term treatment or alternative therapies 3.
- Measurement of TSI bioassay at baseline and follow-up can provide valuable information for clinicians to make informed decisions about treatment strategies and prognosis in patients with Graves' disease 3.