Resistance to thyroid hormone accompanied by atrial fibrillation

Area of Science:

• Endocrinology
• Cardiology
• Genetics

Background:

• Resistance to thyroid hormone (RTH) is a genetic disorder caused by THRB gene mutations, leading to tissue hyposensitivity to thyroid hormone.
• Atrial fibrillation (AF) is a common cardiac arrhythmia, and its association with RTH is rarely reported.
• Managing AF in RTH patients presents challenges due to limited established treatment guidelines.

Purpose of the Study:

• To report a case of RTH coexisting with AF in a young Japanese man.
• To investigate the genetic basis of RTH in the patient.
• To evaluate the efficacy of bisoprolol fumarate in managing AF in this specific clinical scenario.

Main Methods:

• Clinical presentation and diagnostic workup of a 22-year-old male with palpitations and fatigue.
• Hormonal assays including TSH, free T4, and T3 levels.
• Genetic analysis of the THRB gene to identify mutations.
• Electrocardiography to diagnose AF.
• Pharmacological intervention with bisoprolol fumarate for AF management.

Main Results:

• The patient was diagnosed with RTH due to a missense mutation (F269L) in the THRB gene.
• Electrocardiography confirmed atrial fibrillation (AF).
• Treatment with oral bisoprolol fumarate (5 mg/day) successfully restored normal sinus rhythm within one week.
• The patient remained in normal sinus rhythm and asymptomatic for 3 years under bisoprolol therapy.

Conclusions:

• Atrial fibrillation can be a manifestation in patients with Resistance to Thyroid Hormone (RTH).
• Bisoprolol fumarate, a beta-blocker, demonstrated effectiveness in managing atrial fibrillation in a patient with RTH.
• Further research is warranted to establish consensus on AF management strategies in RTH patients.