Some degree of stimulation of the thyroid gland by chorionic gonadotropin (see 118860) is common during early pregnancy. When serum chorionic gonadotropin concentrations are abnormally high, e.g., in women with molar pregnancies (231090), overt hyperthyroidism may ensue. The pathophysiologic mechanism appears to be promiscuous stimulation of the thyrotropin receptor by the excess chorionic gonadotropin. The explanation for this stimulation is the close structural relations between chorionic gonadotropin and thyrotropin and between their receptors (Grossmann et al., 1997). [from
OMIM]