Levothyroxine Treatment and IVF Outcomes in Women With Subclinical Hypothyroidism: A Target Trial Emulation
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- Are you between 18 and 45 years old?
Source: NCT07257250, who can take part
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- Who runs it
- Mỹ Đức Hospital
- Trial code
- NCT07257250
- Record updated
- 14 January 2026
- Original description
Subclinical hypothyroidism (SCH) is defined by elevated thyroid-stimulating hormone (TSH) with normal free thyroxine (fT4) levels. It affects approximately 5-7% of women of reproductive age and may negatively influence outcomes of assisted reproductive technology (ART). During controlled ovarian stimulation, rising estradiol increases thyroxine-binding globulin and thyroid hormone requirements. These physiological changes, combined with increased metabolic demand in early pregnancy, may worsen SCH and contribute to adverse outcomes such as miscarriage, preterm birth, and hypertensive disorders of pregnancy.Read full original descriptionShow less
Effectiveness of Levothyroxine Treatment on In Vitro Fertilization and Pregnancy Outcome in Women With Subclinical Hypothyroidism and Infertility: A Target Trial Emulation
Subclinical hypothyroidism (SCH) is defined by elevated thyroid-stimulating hormone (TSH) with normal free thyroxine (fT4) levels. It affects approximately 5-7% of women of reproductive age and may negatively influence outcomes of assisted reproductive technology (ART). During controlled ovarian stimulation, rising estradiol increases thyroxine-binding globulin and thyroid hormone requirements. These physiological changes, combined with increased metabolic demand in early pregnancy, may worsen SCH and contribute to adverse outcomes such as miscarriage, preterm birth, and hypertensive disorders of pregnancy.
Although levothyroxine (LT4) is routinely used to treat overt hypothyroidism, evidence for its benefit in SCH, especially among infertile women undergoing In Vitro Fertilization (IVF) or Intra-Cytoplasmic Sperm Injection (ICSI) with frozen embryo transfer (FET), remains inconclusive. Some trials and meta-analyses have shown reductions in miscarriage and neonatal mortality, while others have found no improvement in ART or obstetric outcomes.
This study aims to evaluate the effectiveness of levothyroxine therapy on IVF/FET outcomes and subsequent pregnancy results in women with subclinical hypothyroidism and infertility. This retrospective cohort study will emulate the target trial to evaluate whether LT4 treatment, titrated to achieve a pre-transfer TSH < 2.5 mIU/L, improves implantation, live birth, and obstetric outcomes compared with expectant management.
Inclusion: Women aged 18-45 years; Diagnosed with subclinical hypothyroidism (TSH 4.2-<10 mIU/L with FT4 0.92-1.68 ng/dL); Undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) followed by frozen embryo transfer (FET).
Exclusion: Current or recent (within 1 month) use of drugs affecting thyroid function (levothyroxine, amiodarone, methimazole, propylthiouracil); Overt hypothyroidism (TSH ≥10 mIU/L and FT4 ≤0.92 ng/dL).