ABSTRACT
Human chorionic gonadotropin(HCG) is a member of the glycoproteins family synthesized by the placenta, which consists of 2 noncovalently joined subunits(alpha(alpha) and beta(beta)). The alpha- and beta-subunits have a structural homology with the alpha- and beta-subunits of TSH and LH. The thyrotropic action of HCG results from its structural similarity to TSH, so beta-HCG can bind to the TSH receptor in the thyroid gland. A high level of HCG accompanied by an increased thyroid hormone level, can be observed in gestational trophoblastic disease (GTD), such as a hydatidiform mole or a choriocarcinoma, but the clinical symptoms of hyperthyroidism are rarely observed. We experienced a case of Hashimoto's thyroiditis, where the patient was diagnosed with T3-thyrotoxicosis, which had initially been induced by excess beta-HCG due to an H-mole; after evacuation of the H-mole, the condition was diagnosed as hypothyroidism. It has been speculated that a patient with Hashimoto's thyroiditis could have hyperthyroidism, induced by beta-HCG, due to an H-mole