Occasionally, GTD is complicated by hyperthyroidism, which may require treatment. This is thought to occur due to molecular mimicry between human chorionic gonadotrophin (HCG) and thyroid-stimulating hormone (TSH), and hence cross-reactivity with the TSH receptor.

Why does hydatidiform mole cause hyperthyroidism?

Clinical thyrotoxicosis is rare in molar pregnancy and has yet to be reported in a patient with a partial mole. Human chorionic gonadotropin (hCG), which has thyrotropic activity, is believed to be responsible for hyperthyroidism of gestational trophoblastic activity and hyperemesis gravidarum.

Why does hyperthyroidism occur in molar pregnancy?

5 In normal pregnancy, the elevated β-hCG concentration induces a weak hyperthyroid state. This is heightened in molar pregnancy due to higher concentrations of β-hCG.