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. 2025 Mar;102(3):315-323.
doi: 10.1111/cen.15150. Epub 2024 Oct 14.

Treatment of Subclinical Hyperthyroidism and Incident Atrial Fibrillation

Mohammad Jay  1 , Peter Huan  2 , Nikki Cliffe  3 , Jonah Rakoff  3 , Emily Morris  2 , Peter Kavsak  4 , Meera Luthra  5 , Zubin Punthakee  5
Affiliations

Treatment of Subclinical Hyperthyroidism and Incident Atrial Fibrillation

Mohammad Jay et al. Clin Endocrinol (Oxf). 2025 Mar.

Abstract

Context: Treating overt hyperthyroidism prevents atrial fibrillation (AF). Though subclinical hyperthyroidism (SH) has been associated with AF, it is unknown whether treating SH prevents AF.

Objective: We aimed to identify the association between treating SH and incident AF.

Design: In a pharmacoepidemiologic retrospective cohort study, patients diagnosed with SH between 2000 and 2021 were followed.

Patients: Outpatients ≥ 18 years with biochemical SH and without prior AF, hypothyroidism, thyroid cancer, pituitary disease, or pregnancy were included.

Main outcomes: The primary outcome was incident AF. Secondary outcomes were ECG and echocardiographic features associated with AF.

Results: Of 2169 patients screened, 360 (131 treated and 229 untreated) were followed up for a mean of 4.27 years. In the treated and untreated groups, AF occurred in 4 (3.1%) and 15 (6.6%) patients (p = 0.15), and AF incidence was 0.8% and 1.4%/year (p = 0.31), respectively. The hazard ratio (HR) for treatment as a time-dependent variable was 0.60 (95% CI 0.19-1.92; p = 0.39). As some cases of AF were documented nearly simultaneously with SH treatment, a sensitivity analysis was performed reassigning two patients diagnosed with AF < 30 days after starting SH treatment to the untreated group. Here, in the treated and untreated groups, AF occurred in 1.6% and 7.4% (p = 0.02), and AF incidence was 0.4% and 1.8%/year (p = 0.02), respectively. The HR was 0.25 (0.06-1.13; p = 0.07). There were no differences in ECG or echocardiographic features.

Conclusion: There was an overall trend towards lower incidence and prevalence of AF following treatment of SH, supporting the need for larger scale studies.

Keywords: atrial fibrillation; subclinical hyperthyroidism; treatment.

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Conflict of interest statement

Peter Kavsak: Outside of this work, Dr. Kavsak has received grants/reagents/consultant/advisor/honoraria from Abbott Laboratories, Abbott Point of Care, Beckman Coulter, Ortho Clinical Diagnostics, Quidel, Randox Laboratories, Roche Diagnostics, Siemens Healthcare Diagnostics and Thermo Fisher Scientific. McMaster University has the following patent with Dr. Kavsak listed as an inventor: ‘Method of Determining Risk of an Adverse Cardiac Event’. The other authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Participant flow. Each patient was excluded for only one reason. The first exclusion criteria listed were applied.
Figure 2
Figure 2
Extended Kaplan–Meier curve of the probability of atrial fibrillation (AF) development with treatment as a time‐dependent variable.
See this image and copyright information in PMC

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