Pregnant women with low TSH is generally due to the normal hormone level changes during pregnancy, in addition to exclude the existence of pre-pregnancy history of hyperthyroidism and whether the pregnancy is suffering from hyperthyroidism, the specific circumstances should also be combined with the value of T3, T4 to make a comprehensive judgment. 1. Normal physiological response during pregnancy: with the rise in chorionic gonadotropin levels during pregnancy, especially during the 8-10 weeks of pregnancy, HCG levels will reach their peak, and TSH will briefly decrease in the early stages of pregnancy and rise to pre-pregnancy levels at the end of the early stages of pregnancy, and then remain stable, so that transient lows can be treated without special treatment. 2. The existence of hyperthyroidism before pregnancy, with the changes in hormone levels in the body after pregnancy, TSH is also prone to decline, but generally prone to T3, T4 level of abnormality, combined with the specific examination to determine whether there is an abnormality, in addition to hyperthyroidism history of pre-pregnancy it is best to control the normal before pregnancy, and then prepare for the pregnancy. 3. Hyperthyroidism in pregnancy is prone to a decrease in TSH, accompanied by an increase in T3 and T4, and is also prone to panic attacks, irritability and weight loss. It is recommended to go to the hospital to improve the thyroid function, thyroid ultrasound and other related examinations, according to the results of the examination, follow the doctor’s instructions for treatment.