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NCT Number: NCT07380854

Thyroid Hormone Replacement After Coronary Artery Bypass Grafting for Patients With Subclinical Hypothyroidism

The goal of this clinical trial is to find out whether levothyroxine reduces complications and improves the prognosis of patients with subclinical hypothyroidism (SCH) undergoing coronary artery bypass grafting (CABG).

The main questions this study aims to answer are:

• Does levothyroxine reduce major adverse cardiovascular events (MACE), including cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, and new arrhythmias, in SCH patients undergoing CABG? Researchers will compare patients who take levothyroxine with those who do not.

Participants will:

* Be randomly assigned to either receive levothyroxine or not * Start the medication one day before surgery if assigned to the treatment group. * Have regular follow-up visits to check thyroid function and cardiovascular events for up to five years after surgery.

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Key information

Conditions

Subclinical Hypothyroidism

Age range

19 year–90 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Department of Internal Medicine, Seoul National University Bundang Hospital

Seongnam-si, 13620, South Korea

Location status: Recruiting

Location contact

Kang

CONTACT

[email protected]

+82-787-7029

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Eligibility Criteria

  • Adults aged 19 to 90 years.
  • Patients scheduled to undergo coronary artery bypass graft (CABG) surgery.
  • Subclinical hypothyroidism (SCH), defined as a normal free thyroxine (free T4) level and a thyroid-stimulating hormone (TSH) level greater than 4 μIU/mL, based on testing performed within 31 days prior to surgery.

Exclusion criteria

  • Patients who underwent repeat or emergency CABG surgery
  • Use of LT4 within the previous 4 weeks
  • Use of antithyroid drug use (propylthiouracil, methimazole, or carbimazole) within the previous 3 months
  • Severe comorbid conditions with a life expectancy of less than 1 year (e.g. advanced malignancy)

Treatment and study plan

Levothyroxine

Drug

Intervention description: Participants assigned to the LT4 group will begin receiving levothyroxine the day before CABG. The initial dose is 25 μg once daily, or 12.5 μg for participants weighing less than 60 kg. The dose will then be adjusted based on thyroid function test results to achieve target TSH levels of 0.4-2.0 μIU/mL.

Primary outcomes

  1. A composite of MACE within 4months after surgery

    Time frame: within 4months after surgery

    A composite of major adverse cardiovascular events (MACE), including cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, and the occurrence of new arrhythmias assessed within 4 months after CABG.

Secondary outcomes

  1. Number of participants who experience cardiovascular death within 4 months after surgery

    Time frame: within 4months after surgery

    Number of participants who experience cardiovascular death within 4 months after CABG

  2. Number of participants who experience nonfatal myocardial infarction within 4 months after surgery

    Time frame: within 4months after surgery

    Number of participants who experience nonfatal myocardial infarction within 4 months after CABG

  3. Number of participants who experience nonfatal stroke within 4 months after surgery

    Time frame: within 4months after surgery

    Number of participants who experience nonfatal stroke within 4 months after CABG

  4. Number of participants who experience new arrhythmia within 4 months after surgery

    Time frame: within 4months after surgery

    Number of participants who experience new arrhythmia within 4 months after CABG

  5. A composite of MACE within 1 year after surgery

    Time frame: within 1 year after surgery

    A composite of major adverse cardiovascular events (MACE), including cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, and the occurrence of new arrhythmias assessed within 1year after CABG

  6. A composite of MACE within 5 year after surgery

    Time frame: within 5 years after surgery

    A composite of major adverse cardiovascular events (MACE), including cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, and the occurrence of new arrhythmias assessed within 5 years after CABG

  7. All-cause mortality within 5 years after surgery

    Time frame: within 5 years after surgery

    All-cause mortality within 5 years after surgery

  8. Change in LVEF from baseline to 1 year after surgery

    Time frame: From baseline to 1 year after surgery

    Left ventricular ejection fraction (LVEF) will be measured using transthoracic echocardiography at baseline (pre-operative) and at 1 year post-operatively. The outcome will be reported as the mean change in LVEF (%) from baseline to 1 year.

  9. Change in LV EDD from baseline to 1 year after surgery

    Time frame: From baseline to 1 year after surgery

    Left ventricular end-diastolic diameter (LVEDD) will be measured using transthoracic echocardiography at baseline (pre-operative) and at 1 year post-operatively. The outcome will be reported as the mean change in LVEDD (%) from baseline to 1 year.

  10. Change in LV ESD from baseline to 1 year after surgery

    Time frame: From baseline to 1 year after surgery

    Left ventricular end-systolic diameter (LV ESD) will be measured using transthoracic echocardiography at baseline (pre-operative) and at 1 year post-operatively. The outcome will be reported as the mean change in LV ESD (%) from baseline to 1 year.

  11. Change in LVMI from baseline to 1 year after surgery

    Time frame: From baseline to 1 year after surgery

    Left ventricular mass index (LVMI) will be measured using transthoracic echocardiography at baseline (pre-operative) and at 1 year post-operatively. The outcome will be reported as the mean change in LVMI (%) from baseline to 1 year.

  12. Change in LAMI from baseline to 1 year after surgery

    Time frame: From baseline to 1 year after surgery

    Left atrial volume index (LAMI) will be measured using transthoracic echocardiography at baseline (pre-operative) and at 1 year post-operatively. The outcome will be reported as the mean change in LAMI (%) from baseline to 1 year.

Study contacts

Contact information is provided by the study sponsor or research team.

Min Joo Kim, Professor

CONTACT

[email protected]

+82-31-787-7855

Sponsors and collaborators

Lead sponsor

Seoul National University Bundang Hospital

Other

Registry information

Acronym: RepleniSH

Important dates

Study start
2022
Primary completion
2032
Study completion
2037
First posted
Feb 2, 2026
Registry last updated
Feb 2, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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