The study was terminated due to insufficient funding, rendering it impossible to continue purchasing reagents for experiments

The purpose of this clinical trial is to understand the impact of different doses of levothyroxine on the immune inflammatory response in pregnant women with normal-high TSH and positive TPOAb in the first half of pregnancy. It aims to answer the main questions:

Are there differences in immune inflammation between normal pregnant women and those in the disease group? Can different doses of levothyroxine improve the Th17/Treg ratio and cytokine levels in the disease group? Researchers first compared the differences between normal pregnant women and those in the disease group, and then administered two different doses of levothyroxine to the disease group to observe whether different doses of levothyroxine can improve the immune inflammation in this group.

pregnant women in the disease group will: Take the same dose of levothyroxine (25/50ug) every day Return for a follow-up visit after 4 weeks of medication

To explore the correlation between different doses of levothyroxine (LT4) supplementation and Th17/Treg and cytokines in pregnant women with normal-high thyroid stimulating hormone (TSH) and positive thyroid peroxidase antibody (TPOAb) in the first half of pregnancy. From June 2022 to October 2023, 34 pregnant women with high- normal TSH and positive TPOAb in our hospital were selected (disease group), and 30 healthy pregnant women (control group) were matched; the disease group was divided into HA group and HB group according to the administration of 25 ug LT4 and 50 ug LT4. Blood samples were collected from the control group and the disease group before and 4-8 weeks after intervention to detect thyroid function, cytokine and blood lipid levels, flow cytometry to determine the proportion of Th17 and Treg cells, and methane hydrogen blowing examination was performed in parallel; the serological differences between the groups and before and after intervention were compared, and correlation analysis was used to analyze thyroid function, blood lipids, cytokines, and Th17/Treg.

Inclusion Criteria:

• Thyroid function level meets the specific reference range established by the laboratory department of our hospital based on the "Guidelines for the prevention and management of thyroid diseases during pregnancy and perinatal period" : FT4: 12-22pmol/L; disease group: TPOAb>;34IU/mL, TSH: 2.5mIU/L-upper limit of reference range; control group: TPOAb≤34IU/mL, TSH<2.5mIU/L;
• All pregnant women are in the first half of pregnancy (gestational age≤20 weeks).

Exclusion Criteria:

• Combined with hypothyroidism, subclinical hypothyroidism, and hyperthyroidism;
• Assisted reproduction;
• Multiple pregnancy;
• Combined with other autoimmune diseases such as antiphospholipid syndrome and thrombophilia;
• Severe intestinal diseases or intestinal surgery history, or the use of probiotics, prebiotics and other drugs that affect intestinal flora;
• Obesity, pre-pregnancy hyperlipidemia;
• Adverse reactions to LT4

The population that meets the inclusion and exclusion criteria and is willing to participate in the research.