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Introduction to Autoimmune Thyroid Diseases
Autoimmune thyroid diseases (AITDs) encompass a group of disorders characterised by abnormal immune system responses resulting in inflammation and damage to the thyroid gland. The most common forms of AITDs are Graves’ disease (GD) and Hashimoto’s disease (HD).
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Graves’ Disease: GD leads to overactive thyroid function or hyperthyroidism. It is characterised by the presence of thyroid-stimulating immunoglobulins (TSIs), autoantibodies that stimulate excessive production of thyroid hormones.
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Hashimoto’s Disease: HD causes underactive thyroid function or hypothyroidism. In HD, thyroperoxidase antibodies (TPO Abs) attack and destroy cells responsible for producing thyroid hormones.
Genetic Susceptibility in Autoimmune Thyroid Diseases
Research has consistently demonstrated a significant genetic component in AITDs, indicating specific genes play a crucial role in predisposing individuals to these disorders. While environmental factors also contribute, let’s focus on understanding the genetic factors associated with GD and HD susceptibility.
HLA Genes:
Certain variants of human leukocyte antigen (HLA) genes, particularly HLA-DR3 and HLA-DR4, have been consistently associated with an increased susceptibility to GD. Conversely, specific variants of HLA-DR5 have been linked to a higher risk for HD.
CTLA4 Gene:
The cytotoxic T lymphocyte-associated antigen 4 (CTLA4) gene is involved in regulating immune responses by inhibiting T-cell activation. Variants of the CTLA4 gene, particularly the CT60 polymorphism, have been implicated in both GD and HD susceptibility.
PTPN22 Gene:
Certain variants of the protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene have been associated with an increased risk of developing GD and HD.
B7-H3 and B7-H4 Genes (New Findings):
Recent research has highlighted the involvement of B7-H3 and B7-H4, members of the B7 family of proteins, in AITDs (1). These proteins contribute to immune dysregulation observed in Graves’ disease and Hashimoto’s disease.
The results of the study revealed some interesting connections between genetic variations in the B7H3 and B7H4 genes and disease severity in AITDs. For example, they found that individuals with severe HD had a higher frequency of a particular genetic variation called CC genotype of B7H3 rs3816661. This suggests that this variation may contribute to more severe symptoms in HD.
When it comes to the B7H4 gene, they observed that individuals carrying certain variations (G carriers of rs10754339 A/G and rs13505 T/G) were more commonly found among AITD patients compared to healthy controls. This implies that these genetic variations might increase the risk of developing AITDs.
The study also explored whether specific genetic variations in the B7H3 and B7H4 genes were related to differences in disease prognosis among AITD patients. The findings revealed that individuals carrying particular variations (a carrier of rs10158166 A/G and C carriers of rs3806373 C/T) in the B7H4 gene were more frequently seen in those with difficult-to-control GD. Difficult-to-control GD refers to cases where standard treatments fail to effectively manage hyperthyroidism.
Additionally, when looking at soluble forms of these proteins, they discovered intriguing associations with prognosis. For instance, individuals with the CC genotype of B7H3 rs3816661 had a higher proportion of certain immune cells called B7-H3+ monocytes, indicating a potential role in disease progression. Furthermore, the concentration of soluble B7-H4 was higher in AITD patients compared to healthy controls, and it varied based on the variation of rs13505 T/G (1).
Genetic Testing and Personalised Medicine
Understanding the genetic basis of AITDs opens up possibilities for tailored diagnostic approaches and personalised treatment strategies. Genetic testing can help identify individuals at higher risk for developing GD or HD, allowing for early intervention and monitoring. It can also aid in predicting disease severity, response to medication, and potential complications.
Genetic information can guide physicians in selecting the most appropriate treatment options, such as determining the optimal dosage of medication or considering alternative therapies based on an individual’s genetic profile. This personalised approach holds promise for improved patient outcomes and reduced side effects.
The Future of Genetics in AITDs Research
Research into the genetics of AITDs is an ever-evolving field, with ongoing studies seeking to unravel additional genes involved in disease susceptibility and prognosis. Developments in genome-wide association studies and advanced sequencing technologies are expected to uncover further insights into the complex interplay between genetics, environmental factors, and immune dysregulation.
The ultimate goal is to develop targeted therapies that address specific genetic abnormalities associated with AITDs. By understanding the intricate mechanisms behind these disorders at a molecular level, researchers are paving the way for more effective treatments and potentially even preventive strategies.
In conclusion, genetics plays a vital role in autoimmune thyroid diseases such as Graves’ disease and Hashimoto’s disease. Certain genes contribute to susceptibility while others affect prognosis and clinical outcomes. With advancements in genetic testing and personalised medicine, healthcare professionals have a unique opportunity to tailor treatment approaches according to an individual’s genetic profile. The ongoing research in this field holds immense potential for future advancements in diagnosis, treatment, and prevention of AITDs.
References:
- Ozaki H, Inoue N, Iwatani Y, Watanabe A, Yamamoto M, Kitahara N, Tanikawa S, Noguchi Y, Hidaka Y, Watanabe M. Association of B7H3 and B7H4 gene polymorphisms and protein expression with the development and prognosis of autoimmune thyroid diseases. Clin Endocrinol (Oxf). 2023 Jul;99(1):103-112.
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Inna Kurlyandchik | BHSc (Naturopathy), Grad Cert Nutr, PhD candidate
Unveiling the Role of Genetics in Autoimmune Thyroid Diseases
In this blog post, we will explore the fascinating connection between genetics and autoimmune thyroid diseases (AITDs), focusing on two common disorders: Graves’ disease (GD) and Hashimoto’s disease (HD). We will delve into the underlying genetic factors that contribute to the susceptibility and prognosis of these disorders. By understanding the role of genetics in AITDs, we can gain valuable insights into potential diagnostic tools and personalised treatment approaches.
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