Graves Disease With Thyroid-Stimulating Hormone Receptor–Blocking Autoantibodies During Pregnancy

Graves Disease With Thyroid-Stimulating Hormone Receptor–Blocking Autoantibodies During Pregnancy:Background: Graves disease is an autoimmune disease caused by thyroid-stimulating hormone receptor antibodies (TSH-R-Ab), which can be stimulating (TSAb), neutral, or blocking (TBAb). The net antibody activity determines the clinical phenotype. Typically, TSAbs dominate, resulting in hyperthyroidism. Rarely, TBAbs prevail, resulting in hypothyroidism (1). The conventional TSH-R-Ab binding assay used in clinical practice does not differentiate among antibody types. This limitation is relevant in women with Graves disease who are taking L-thyroxine (L-T4) and become pregnant because TSH-R-Abs cross the placenta and affect the fetal thyroid gland.