Abstract
Background: TSH receptor (TSHr)-stimulating immunoglobulins (Igs) can be used as diagnostic markers of Graves’ disease (GD). Thyroid-stimulating immunoglobulin (TSI) assays exclusively detect these specific Igs. Materials and Methods: This was a prospective longitudinal study in which hyperthyroid patients with GD and toxic nodular goitres were evaluated at diagnosis. GD patients were also evaluated at antithyroid drug (ATD) withdrawal. An automated chemiluminescent assay measured TSI. According to the manufacturer TSI less than 0.55 IU/L was a non-reactive result. The authors evaluated the Se and Sp of the cutoff point provided by the TSI assay manufacturer, and tested other cutting points through a ROC curve, to assess relapse risk of Graves’ disease. Results: At diagnosis, were evaluated 92 (85.2%) GD patients aged 41.2 ± 2.0 years, and 16 patients (14.8%) with toxic multinodular goiter (TMNG) or toxic adenoma (TA), aged 60.8 ± 4.8 years. They were re-evaluated after 18 ± 4 months with methimazole (MMI) treatment. The follow-up after treatment suspension was of 20 ± 6 months. At diagnosis, the TSI (Se) and (Sp) were 98.9% and 100%, respectively. At ATD withdrawal, despite a high Se (95.5%), Sp was low (59.6%). By adjusting the cut-off to 1.11 (TSI <1.11 IU/L non-reactive), TSI presented the best Sp (89.4%) with a small decrease in Se (93.3%) in predicting GD relapse. Conclusions: TSI had high Se and Sp in GD differential diagnosis with nodular goiters. In the assessment for GD relapse, by raising the cutting point to 1.11 IU/L, a better Sp was obtained at the expense of a small drop in Se. A larger sample is needed to support a higher TSI cut-off point in the clinical routine to assess GD relapse after ATD.
Highlights
Hyperthyroidism is a consequence of excessive thyroid hormone production by the thyroid gland
This study aimed to evaluate, prospectively, autoimmunity before treatment for Graves’ disease (GD) toxic multinodular goiter (TMNG) and toxic adenoma (TA), and recurrence risk and at the end of treatment with antithyroid drug (ATD) for GD, through Thyroid-stimulating immunoglobulin (TSI) measurement
Of the remaining 119 who started the study, 11 did not complete: four because of nonadherence to treatment; two because they moved to another city; one became pregnant; and four due to the difficulty in controlling hyperthyroidism with ATD
Summary
Hyperthyroidism is a consequence of excessive thyroid hormone production by the thyroid gland. GD is an autoimmune disease mediated by immunoglobulins (Igs) that activate the TSH receptor (TSHr) This leads to TSH-independent thyroid hyperplasia and unregulated thyroid hormone (TH) production and secretion, usually accompanied by goiter [3]. It follows in frequency as causes of hyperthyroidism, toxic multinodular goiter (TMNG) and toxic adenoma (TA), that become autonomous producing TH independent of stimulus from either TSH or TSHr antibodies [4, 5]. The authors evaluated the Sensitivity (Se) and Specificity (Sp) of the cutoff point provided by the TSI assay manufacturer, and tested other cutting points through a ROC curve, to assess relapse risk of Graves’ disease. A larger sample is needed to support a higher TSI cut-off point in the clinical routine to assess GD relapse after ATD
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