Thyroid stimulating antibodies (sTRAb) don't destroy thyroid tissue. To the contrary, they have a TSH-like effect on thyrocytes and therefore lead to hyperthyroidism and thyroid growth resulting in goiter. The exception is Graves' disease with Hashimoto component. Here, the thyroid is also affected by cytotoxic T cells and antibodies directed against thyroid peroxidase, which gives rise to destruction of the thyroid. But even in this case, it aren't the sTRAb, which destroy tissue.
Perhaps healthy tissues refers to extrathyroidal tissues. Due to unknown reasons several tissues including skeletal muscle, heart muscle, adipose tissue and skin have TSH receptors, and they are affected by sTRAb, too. Hypertrophy results from cross-talk of TSH receptors with IGF-1 receptors in Graves' disease.
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