A Rare Case of Complete Heart Block Secondary to Non-Autoimmune Non-Familial Form of Thyrotoxicosis
https://doi.org/10.15605/jafes.041.S1
- Author:
Ket Meng Chin
1
;
Katherine Khor
2
;
Nor Azmi Kamaruddin
3
Author Information
1. Department of Internal Medicine, Hospital Tuanku Fauziah
2. Department of Endocrinology, Hospital Tuanku Fauziah
3. Department of Cardiology, Institut Jantung Negara
- Publication Type:Journal Article
- MeSH:
Thyrotoxicosis;
Heart Block
- From:
Journal of the ASEAN Federation of Endocrine Societies
2026;41(S1):106-107
- CountryPhilippines
- Language:English
-
Abstract:
Introduction:Thyrotoxicosis typically manifests as a hypermetabolic state
characterized by tachyarrhythmias, such as sinus tachycardia or atrial fibrillation. Bradyarrhythmia, specifically
atrioventricular block (AVB), is a rare and atypical cardiac
manifestation. While Graves’ disease is the leading cause
of hyperthyroidism, non-autoimmune etiologies must be
considered when thyroid-stimulating antibodies are absent.
The exact mechanism for AVB in thyrotoxicosis remains
unclear but may involve myocardial inflammation of the
conduction system or autonomic dysfunction.
Case:A 16-year-old male with no previous medical history
presented with a sudden syncopal attack. Clinical evaluation
revealed a complete heart block (CHB) in association
with biochemical evidence of thyrotoxicosis, requiring
a temporary transcutaneous pacemaker insertion. There
were no features of Graves’ disease, such as exophthalmos
and thyroid acropachy, and further investigation showed
a negative thyroid receptor antibody (TRAb) titer
with no family history of thyroid disorders. Thyroid
ultrasonography showed increased vascularity, while
scintigraphy imaging showed diffuse, homogeneous, and
increased uptake in both thyroid lobes. The combination of negative serology and the absence of a family history, along
with a hyperfunctional state on imaging, likely suggests
a rare presentation of sporadic, non-autoimmune, nonfamilial form of thyrotoxicosis. Following the initiation
of anti-thyroid therapy, the CHB completely resolved
without the need for further cardiological intervention. He
achieved a complete clinical remission after a few months
and is being planned for radioactive iodine therapy.
Conclusion:Most of the thyrotoxicosis-associated CHB reported in
the literature was due to Graves’ disease or some forms
of autoimmune thyrotoxicosis, with auto-antibodies and
activated lymphocytes having a role in the pathogenesis
of the CHB. CHB in association with a non-autoimmune,
non-familial form of thyrotoxicosis is indeed rare, and as
this case illustrates, it completely went into spontaneous
sinus rhythm upon initiation of conventional anti-thyroid
therapy. This rare presentation of CHB is believed to have a
benign clinical course.
- Full text:2026080417114294688EP_A156.pdf
