High thyroid hormones during pregnancy may be associated with markedly elevated serum human chorionic gonadotropin (hCG) levels, i.e., transient hyperthyroidism of pregnancy. Transient hyperthyroidism of pregnancy mainly occurs in the early stage of pregnancy, during which the serum human chorionic gonadotropin (hCG) level of pregnant women is significantly elevated. Since hCG has the same α-subunit as TSH, it can stimulate the TSH receptors on the surface of the thyroid gland, resulting in an increase in thyroid hormones (FT4, FT3) and a decrease in TSH. Patients with transient hyperthyroidism in pregnancy mainly present with gastrointestinal symptoms such as severe nausea and vomiting, while hyperthyroidism is relatively mild and usually does not require antithyroid drug (ATD) treatment, only symptomatic supportive treatment (correction of dehydration and electrolyte disorders, etc.) can be given. As the months of pregnancy increase, the hCG level gradually falls back, and the thyroid function can return to normal on its own. Pregnant women with high thyroid hormone levels may also have a combination of Graves’ disease, and it is recommended that they seek medical attention in a timely manner and be treated under a doctor’s supervision.