The triple thyroid function, referred to as triple thyroid function, mainly includes free FT3 (serum free triiodothyronine), free FT4 (serum free thyroxine) and TSH (thyroid stimulating hormone). If a pregnant woman has primary hypothyroidism, there may be a decrease in FT3 and FT4, resulting in a weakening of TSH negative feedback, which causes the pituitary gland to secrete more TSH, resulting in an increase in TSH. In this case, timely replacement therapy is needed to maintain thyroid function within the normal range, such as TSH <2.5µIU/ml, which is safer for the fetus. If hypothyroidism is detected during pregnancy, further thyroid antibody and thyroid ultrasound tests should be performed. If the thyroid antibody test, TGAb (anti-thyroglobulin antibody) and TPO-Ab (anti-thyroid peroxidase antibody) are significantly elevated and the thyroid gland is lattice-like or diffusely enlarged, it is considered to be caused by Hashimoto's thyroiditis. Hypothyroidism management is a long term management and requires timely and regular review of thyroid function throughout pregnancy.