Currently, there are more and more patients with hypothyroidism during pregnancy, and most of them choose to apply eugenol therapy. What is the appropriate level of thyroid stimulating hormone (TSH) to be controlled by oral eugenol? For pregnant patients, HCG secretion increases significantly in early pregnancy, so TSH level decreases in early pregnancy and reaches the lowest value around 10-12 weeks of pregnancy, the decrease is 30%-50% of the trough value, and the median TSH is about 0.8; later TSH value gradually rises and reaches the high limit value around 33 weeks; TSH level increases before delivery. Because of this characteristic of TSH during pregnancy, we believe that we should not use the TSH range of the general population to measure TSH levels during pregnancy; if we use the criteria of the general population, it may lead to misdiagnosis and underdiagnosis. We should have normal ranges of TSH that are specifically applicable to pregnant women, and the TSH ranges should be different for different gestational weeks. In pregnant women, if subclinical hypothyroidism is diagnosed, it should be treated, and it is recommended to control it below 2.5 mIU/L in the first trimester because in early pregnancy, the fetal thyroid gland is not yet developed, and all the thyroid hormones needed for fetal growth and development come from the mother. This period is a critical period for the development of the fetal brain and nervous system, so it is necessary to ensure an adequate supply of thyroid hormones from the mother, otherwise it will affect the intellectual development of the fetus and lower the IQ; in the second six months, it is recommended to control it below 3.5, because the fetus can secrete some thyroid hormones by itself at this time. However, it should not be oversupplemented. If the TSH is too low after maternal treatment, resulting in hyperthyroidism, it will instead increase the rate of preterm delivery and miscarriage. Therefore, the treatment target for pregnant patients is set at 0.5 mIU/L-2.5 mIU/L (especially in the first 3 months of pregnancy). Therefore, according to the different thyroid hormone requirements of pregnant patients, we apply eugenol therapy with the target of thyroid stimulating hormone (TSH) 0.1-2.5 mIU/ L in the first trimester; 0.2-3.0 mIU/ L in the middle trimester; and 0.3-3.0 mIU/ L in the late trimester.