Answer:
The thyroid stimulating immunoglobulin in Graves disease is an antibody to the membrane receptors of thyroid cells that bind TSH.
Step-by-step explanation:
Graves disease is an auto-immune disease in which antibodies produced by one's own body attacks the thyroid gland.
When pituitary gland is stimulated by TRH i.e. thyrotropin releasing hormone from hypothalamus, it releases TSH i.e thyroid stimulating hormone. TSH then goes and binds to the receptors on thyroid cells and stimulate the release of T3 and T4 thyroid hormones. In case of graves disease the antibody binds at the same site as TSH thereby continuously giving signal for the release of T3 and T4 thyroid hormones. This results in hyperthyroidism.