Allison Sayre, MSN, WHNP
Autoimmune thyroid diseases (AITD), most notably Hashimoto’s thyroiditis and Graves’ disease, represent the most prevalent autoimmune endocrine disorders, affecting up to 10% of the world’s population. [1] While genetic predisposition has long been recognized as a significant factor in the development of AITD, emerging research is starting to provide evidence that environmental influences, particularly viral infections, may also play a role. [2] In this article, we will focus on the effects of latent viruses on the thyroid, and we will also dive into the science surrounding Natural Killer (NK) cells and their role in resolving these silent invaders.
Understanding Latent Infections
Let’s start off by briefly defining latent viruses. Latent viruses are viruses that persist in the host in a dormant state, after the initial infection has resolved. Unlike active infections, latent viruses do not produce symptoms or cause immediate harm. They can remain hidden within host cells for extended periods, escaping detection and elimination by the immune system. Common examples of latent viruses include herpesviruses, such as Epstein-Barr virus (EBV), enterovirus, Hepatitis C, and cytomegalovirus. Under certain circumstances, like when the immune system is compromised, these infections can reactivate and trigger both symptoms and disease. [3]
Latent Infections and the Immune System
Viral infections often induce an immune response that is essential for clearing the infection itself, but in some circumstances, a poor immune response can result in adverse immune reactions that target the host, thus leading to the development of certain autoimmune diseases. Latent viruses, in particular, induce an autoimmune response via different mechanisms, including molecular mimicry, bystander activation and epitope spreading. Research has proposed that these are the mechanisms at play in the development of viral-induced autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, and type 1 diabetes. [3]
Latent Infections and the Thyroid
So, what does that mean for the thyroid? Well, based on what science is telling us about the potential role latent viruses play in the development of the autoimmune diseases listed above, it is reasonable to infer that the thyroid would not be immune (pun intended!) to these consequences. In fact, research is pointing to EBV as a potential offender, suggesting that EBV infects B cells and epithelial cells near the thyroid, leading to an immune response that mistakenly targets thyroid tissue, leading to an increased production in thyroid hormone and thyroid antibodies. [1], [4]
One study looked at thyroid tissue collected via core needle biopsy from 35 patients with AITD and 18 patients in a control group. Results showed 40 of 53 samples carrying one or more latent viruses including EBV, enterovirus, cytomegalovirus, and herpesvirus 6. While it remains unclear whether the detected viruses represented causal agents, possible cofactors or simple bystanders, the study does support latent viruses as being a potential trigger for AITD, and it also suggests that viruses, other than EBV, may be implicated in thyroid disease. [2]
The Power of NK Cells
Natural Killer (NK) cells are a type of innate immune cell that play a crucial role in the body's defense against infections. Unlike other immune cells, NK cells can recognize and destroy certain infections without prior sensitization, while leaving healthy cells unscathed. As their name implies, they induce apoptosis (or kill target cells) by recognizing and eliminating the cells through the release of cytotoxic granules. This release of cytotoxins not only prevents the reactivation of latent viruses, but it also enhances the overall immune response.[5], [6]
With their unique ability to manage latent infections and maintain a balanced immune response, NK cells could play a significant role in both preventing and treating thyroid dysfunction. Investigating the therapeutic potential of modulating NK cell activity could pave the way for novel treatments for AITD diseases and other autoimmune conditions influenced by latent infections.[7]
Conclusion
While genetic predisposition is a known factor in AITDs such as Hashimoto’s thyroiditis and Graves’ disease, latent viruses, such as EBV, enterovirus, and cytomegalovirus, are beginning to gain recognition. These viruses can remain dormant in the body and reactivate under certain conditions, potentially triggering thyroid dysfunction and other autoimmune conditions. The involvement of NK cells in managing these infections offers a promising avenue for future research. By harnessing the unique capabilities of NK cells to control latent infections and modulate immune responses, new therapeutic strategies for preventing and treating thyroid dysfunction may be unlocked. Continued research into the mechanisms and interactions of latent viruses and NK cells is important in advancing our understanding and developing innovative treatments for autoimmune thyroid diseases.
Allison Sayre, MSN, WHNP specializes in women's health and functional medicine, blending both traditional and integrative approaches. With over 17 years of experience, she has empowered women to reclaim their health through personalized nutrition and supplementation, hormone balancing, and lifestyle modifications. She received her Bachelor of Science from Mount Carmel College of Nursing and her Master of Science from the University of Cincinnati. She has been a certified women’s health nurse practitioner since 2014 and has continued her education and training in functional medicine from both the Institute of Functional Medicine as well as the American Academy of Anti-Aging Medicine.