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It’s been five years since the first appearance of COVID-19, but the United States is expected to continue experiencing elevated levels of COVID-19 activity at various times going forward. COVID-19 has not only affected global health through direct viral infections but has also raised questions about the potential impact of both the virus and its vaccines on various autoimmune conditions, including thyroid disorders. Recent research from 2024 and 2025 has provided new insights into the complex relationships between COVID-19 vaccination, COVID-19 infection, Hashimoto’s thyroiditis, and hypothyroidism. In this article, we review some of the most relevant findings.
How do COVID-19 vaccination and boosters affect thyroid disease? In general, research has shown that COVID-19 vaccination does not increase your risk of thyroid disease. A nationwide cohort study published in January 2025 specifically stated that COVID-19 vaccination is not associated with an increased risk of thyroid disease.
According to research findings, COVID-19 vaccination can also help preserve thyroid function stability in patients with hypothyroidism who later get a SARS-CoV-2 infection. If you are vaccinated, your thyroid function is likely to remain more stable after COVID compared to people who are unvaccinated.
Worsening of existing hypothyroidism
It’s not all clear sailing, however. COVID-19 vaccination could, in some cases, worsen existing hypothyroidism.
One South Korean study found that the first dose of COVID-19 vaccines was associated with an increased potential risk of worsening pre-existing hypothyroidism. This effect was not observed with the second dose; however, it suggested a possible adaptive response.
This worsening of hypothyroidism may occur due to several mechanisms:
Autoimmune response
Research has shown that vaccination may trigger an immune response in some people, leading to increased production of autoimmune thyroid antibodies. This can result in further damage to the thyroid gland and worsen hypothyroidism.
Research has also shown that vaccinated Hashimoto’s thyroiditis patients show a higher incidence of thyroid-stimulating hormone (TSH) increase (11.9%) compared to a control group without Hashimoto’s (6.1%). These results suggest that COVID-19 vaccination may induce changes in thyroid function in individuals with pre-existing Hashimoto’s thyroiditis.
Inflammatory reaction
The vaccine-induced immune response may cause inflammation in the thyroid gland, potentially affecting its function and exacerbating hypothyroidism symptoms.
Hormonal imbalance
In some cases, vaccination may temporarily disrupt the balance of thyroid hormones, leading to a worsening of hypothyroid symptoms.
It’s important to note that while worsening of existing hypothyroidism has been reported, it appears to be a rare occurrence. Most individuals with hypothyroidism can safely receive COVID-19 vaccines without experiencing significant thyroid-related complications.
Emerging evidence suggests that COVID-19 infection itself may act as a trigger for the development or worsen autoimmune thyroid conditions. This link highlights the complex relationship between viral infections, immune dysregulation, and thyroid health.
A recent study compared COVID-19 survivors to age- and sex-matched controls, uncovering several concerning findings:
- Doubling of autoimmune thyroid disease prevalence: The prevalence of autoimmune thyroid disease was doubled in COVID-19 survivors compared to controls. (This included both Hashimoto’s and Graves’ disease.)
- Increased thyroid autoantibodies: 15.7% of COVID-19 patients had positive thyroid peroxidase antibodies (TPOAb) compared to 7.7% in the control group.
This increased prevalence of thyroid autoimmunity in COVID-19 survivors suggests that COVID-19 infection may play a role in drawing out or increasing thyroid autoimmunity.
Coronavirus disease has been shown to impact various organs and systems in the body, including the thyroid gland. Researchers believe the virus may affect the thyroid directly, through interaction with thyroid cells and indirectly, by altering the immune response. These mechanisms can potentially lead to thyroid dysfunction, including the development or worsening of autoimmune thyroid diseases in predisposed individuals.
Direct effects on the thyroid gland
The virus that causes COVID-19 uses the angiotensin-converting enzyme 2 (ACE2) receptor to enter human cells. Interestingly, thyroid cells express a significant amount of ACE2 receptors, making the thyroid gland a potential target for the virus. When the virus binds to these receptors, it may cause direct damage to thyroid tissue.
COVID-19-related inflammation in the thyroid may also disrupt normal hormone production, potentially leading to conditions such as thyrotoxicosis (overactive thyroid) or hypothyroidism.
In addition to directly affecting thyroid cells, COVID-19 can dysregulate the immune system, contributing to thyroid problems. Several immune-mediated mechanisms are thought to be involved:
- Molecular mimicry: The structure of certain viral proteins may resemble thyroid proteins. This similarity could confuse the immune system, leading it to mistakenly attack the thyroid gland. This phenomenon, known as molecular mimicry, is a potential trigger for autoimmune thyroid diseases such as Hashimoto’s thyroiditis or Graves’ disease.
- Bystander activation: COVID-19 may activate autoreactive T-cells, immune cells that inadvertently attack the body’s tissues. This activation can occur as the immune system responds aggressively to the virus, inadvertently targeting the thyroid and other tissues in the process.
- Release of thyroid antigens: In severe cases of COVID-19, tissue damage caused by inflammation may release thyroid antigens into the bloodstream. These antigens can prompt an immune response against the thyroid gland, further contributing to autoimmune conditions.
The long-term effects of COVID-19 on thyroid health have become a growing area of concern. Research indicates an increased prevalence of thyroid autoimmunity in COVID-19 survivors, making continuous monitoring of thyroid function essential. This is particularly important for those with pre-existing thyroid conditions or risk factors for autoimmune thyroid diseases, such as a family history of thyroid issues or coexisting autoimmune disorders.
Regular screening should include thyroid antibody and function tests to detect potential issues early. These tests help identify abnormalities such as elevated thyroid antibodies, which may indicate the development of autoimmune thyroiditis. By identifying emerging thyroid dysfunctions early, healthcare providers can intervene before symptoms worsen or complications arise, helping to ensure a better clinical outcome. Early detection and management of thyroid disorders reduce the risk of progression to more severe conditions, such as hypothyroidism or hyperthyroidism, both of which can significantly impact overall health and quality of life.
For COVID-19 survivors, particularly those experiencing lingering symptoms or those classified as “long-haulers,” thyroid dysfunction should not be overlooked. The stress of illness, combined with potential immune system changes triggered by the virus, may contribute to the development of thyroid issues. Regular follow-up with a healthcare provider and proactive thyroid management strategies are key to ensuring long-term well-being.
COVID-19 vaccines have proven to be safe and effective for the majority of the population, including individuals with thyroid disorders. However, certain precautions may help minimize potential complications and ensure optimal thyroid health during and after protective coronavirus vaccines for those with existing thyroid conditions.
First, monitoring thyroid function before and after receiving the vaccine is advisable. This is especially relevant if you are a vaccinated person with Hashimoto’s thyroiditis, Graves’ disease, and those who are taking thyroid hormone replacement therapy. Tracking thyroid function markers, including TSH, free T4, free T3 levels, and thyroid antibody levels, can help detect any changes that might occur due to the vaccination.
Second, adjusting thyroid medication doses may be necessary if you experience post-vaccination changes in thyroid function. For instance, the immune response stimulated by the vaccine could temporarily impact your thyroid hormone levels or worsen your underlying thyroid imbalances. Close communication with your healthcare provider can ensure timely medication adjustments to maintain stability.
It’s important to note that while vaccines can occasionally lead to mild, temporary changes in thyroid function due to an activated immune response, many practitioners consider that the benefits of vaccination outweigh the risks. Protecting against severe COVID-19 is critical, particularly for thyroid patients who may be at higher risk of complications from the virus due to other health factors.
In conclusion, both long-term monitoring and proactive measures surrounding vaccination are crucial for COVID-19 survivors and individuals with thyroid disorders. Regular thyroid screenings and adjustments to treatment plans, as needed, can help maintain optimal thyroid function and overall health. For thyroid patients, these steps ensure that your condition remains well-managed while you stay protected against COVID-19.
More comprehensive studies are needed to better understand the long-term impact of COVID-19 and its vaccines on thyroid function.
- Tracking thyroid function and autoimmunity markers in large cohorts of COVID-19 survivors over extended periods.
- Investigating the potential differences in thyroid effects among various COVID-19 vaccine types.
Further research is also needed to elucidate the precise mechanisms by which COVID-19 and its vaccines may influence thyroid function. Specifically, there’s a need for :
- Molecular studies to identify potential cross-reactivity between COVID-19 antigens and thyroid tissues.
- Investigation of the role of vaccine ingredients in triggering or modulating thyroid autoimmunity.
The relationship between COVID-19, its vaccines, and thyroid function is complex and still not fully understood. While there is evidence of increased thyroid autoimmunity and potential worsening of existing thyroid conditions following COVID-19 infection or vaccination, the overall risk appears low for most individuals. The benefits of COVID-19 vaccination in preventing severe disease and complications likely outweigh the potential risks of thyroid dysfunction for the majority of patients.
As our understanding of these interactions continues to evolve, ongoing research and vigilant clinical monitoring will be crucial in optimizing care for individuals with or at risk for thyroid disorders in the context of the ongoing presence of COVID-19. Healthcare providers should remain alert to the possibility of thyroid dysfunction in COVID-19 survivors and vaccinated individuals. At the same time, patients Paloma encourages you to monitor for and evaluate any concerning symptoms and communicate them to knowledgeable healthcare providers.
Ultimately, personalized approaches to patient care, taking into account your individual risk factors and medical histories, will be essential in navigating the complex interplay between COVID-19, vaccination, and thyroid health.
When you have a pre-existing thyroid condition, it’s helpful to discuss whether the benefits of COVID-19 vaccination outweigh the risks for your own health with your healthcare provider. Paloma Health’s knowledgeable providers can offer guidance and help you decide.
After COVID-19 vaccination, boosters, or COVID-19 infection, you’ll want to monitor your potential thyroid symptoms and report any new or worsening symptoms that may be related to your thyroid function to your healthcare providers.
It’s essential to regularly monitor your thyroid function, especially after COVID-19 infection, vaccination, or boosters. Paloma’s complete thyroid test kit makes this affordable and convenient to do from the comfort of your home.
Paloma also has other resources to help you understand the COVID-19-thyroid connection.
For those who have developed significant symptoms after a COVID-19 infection, we recommend this video webinar, “Long Haul COVID & Its Impact on Thyroid Health.”
- Research confirms that COVID-19 vaccination does not increase the risk of developing thyroid disorders and may help stabilize thyroid function in patients with hypothyroidism after COVID-19 infection.
- Rare cases of worsening hypothyroidism after the first vaccine dose have been reported, potentially linked to autoimmune responses, inflammatory reactions, or temporary hormonal imbalances.
- Studies show COVID-19 infection may trigger or worsen autoimmune thyroid diseases like Hashimoto’s and Graves’ disease, with a higher prevalence of thyroid autoantibodies in COVID-19 survivors compared to controls.
- COVID-19 impacts the thyroid gland through mechanisms like ACE2 receptor binding, inflammation, and immune dysregulation, potentially leading to conditions like thyrotoxicosis or hypothyroidism.
- Regular thyroid function and antibody tests are crucial for COVID-19 survivors and individuals with thyroid disorders, especially after infection or vaccination, to detect changes early and prevent complications.
- Monitoring thyroid markers before and after vaccination and adjusting medications as needed can help maintain thyroid stability while benefiting from vaccination’s protection against severe COVID-19.
- COVID-19 survivors, particularly “long-haulers,” should prioritize thyroid health through regular follow-ups to address potential dysfunctions arising from illness or immune changes.
- Further studies are needed to understand the long-term impact of COVID-19 and its vaccines on thyroid health, including molecular mechanisms and differences among vaccine types.
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