If it is determined that there is no history of hyperthyroidism before pregnancy, there is no need to be overly alarmed if thyroid hormones are found to be elevated in early pregnancy. You should be familiar with chorionic gonadotropin (hCG), but you may not know that hCG is structurally similar to thyroid stimulating hormone (TSH, which promotes thyroid secretion and plays an important role in the growth and metabolism of the thyroid gland itself), so hCG also has a certain role in promoting thyroid hormone secretion. In the third trimester, hCG secretion reaches its peak and stimulates the thyroid gland to secrete more thyroid hormone, which is called “transient hyperthyroidism in pregnancy”. How to distinguish transitory hyperthyroidism in pregnancy from true hyperthyroidism? Professor Ma said that transient hyperthyroidism in pregnancy can be characterized by severe nausea, vomiting, weight loss, and in severe cases, dehydration and ketosis (prolonged starvation resulting in a serious lack of energy intake, the body mobilizes fat and protein hydrolysis to provide energy, resulting in an increase in acetone in the metabolites and a syndrome similar to diabetic ketosis), but without the typical symptoms of hyperthyroidism such as goiter and proptosis. The thyroid excitatory antibodies (TRAb) and anti-thyroid peroxidase antibodies (TPOAb) are negative. In first-trimester hyperthyroidism, symptomatic treatment is the mainstay, and most of them do not require anti-thyroid medication. By the middle of pregnancy, the hCG level will gradually decrease and the thyroid hormone will slowly return to normal, and the clinical symptoms will disappear. However, thyroid stimulating hormone (TSH) returns to normal generally 1-2 months later than thyroid hormones (T4, T3). You may also be concerned that transient hyperthyroidism in pregnancy will not become true hyperthyroidism. In fact, most pregnant women have a peak in serum hCG that lasts only a few days and does not usually lead to hyperthyroidism. Most patients who are diagnosed with true hyperthyroidism after pregnancy often had hyperthyroidism before pregnancy but did not pay attention to it and only discovered it during maternity testing. Of course, pregnancy is also an autoimmune process, and hyperthyroidism may occur during pregnancy if fever, infection, insomnia, or intense mood swings occur, but pregnancy alone will not induce hyperthyroidism.