Hashimoto disease (HD), also known as Hashimoto’s thyroiditis, is an autoimmune condition in which the immune system mistakenly attacks the thyroid gland.
The thyroid gland is a small, butterfly-shaped gland located in the neck that produces hormones regulating metabolism, heart rate, and body temperature. In HD, chronic inflammation damages the thyroid, leading to reduced hormone production, a condition called hypothyroidism.
This condition is more common in women and often develops gradually, with symptoms such as fatigue, weight gain, sensitivity to colds, hair loss, and depression. Diagnosis is typically made through blood tests measuring thyroid hormone levels and the presence of thyroid antibodies. While Hashimoto’s disease cannot be cured, its associated hypothyroidism can be managed with synthetic thyroid hormones to restore normal hormone levels.
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Hashimoto disease and hypothyroidism are closely related but not the same. Hashimoto disease is an autoimmune disorder where the immune system attacks the thyroid gland, leading to inflammation and gradual thyroid dysfunction. This destruction over time results in hypothyroidism, a condition where the thyroid cannot produce sufficient hormones to regulate the body’s metabolism.
In other words, HD is the cause, while hypothyroidism is the effect. Not all hypothyroidism is caused by Hashimoto’s. Other factors, such as iodine deficiency or certain medications, can also lead to an underactive thyroid. Hashimoto’s is one of the most common causes of hypothyroidism in developed countries.
Researchers often study HD along with another autoimmune thyroid condition called Grave’s disease (GD). HD and GD affect the thyroid gland in opposite ways. In contrast to HD, Graves’ disease causes the immune system to overstimulate the thyroid, leading to hyperthyroidism, where the thyroid produces too much hormone. This results in symptoms such as weight loss, rapid heartbeat, and anxiety.
Hashimoto disease is the most common cause of hypothyroidism in many parts of the world, especially in areas with sufficient iodine intake. It affects an estimated 5% of the general population, with a higher prevalence in women than men. Women are about 7-10 times more likely to develop Hashimoto’s, particularly between the ages of 30 and 50. The prevalence of HD tends to increase with age, and it is more common in individuals with a family history of thyroid or autoimmune disorders.
While it can occur in men and children, it is significantly rarer in those groups. Environmental factors, such as excessive iodine intake, radiation exposure, and chronic stress, can also influence the development of HD. Genetic predisposition plays a strong role, but lifestyle and environmental factors may also contribute.
Hashimoto disease has a strong genetic component, as it tends to run in families. Studies have identified several genetic markers associated with increased susceptibility to autoimmune thyroid diseases, including Hashimoto’s. A 2021 population-based twin study put the heritability estimate of this condition at 65%.
Multiple genes have been identified as being linked to the onset, progression, and severity of the disease. Key gene variants include those related to human leukocyte antigen (HLA), cytotoxic T lymphocyte antigen-4, protein tyrosine phosphatase non-receptor type 22, thyroglobulin, the vitamin D receptor, and various cytokines, all of which are regarded as highly significant for this condition.
HLAs (human leukocyte antigens) are coded by a group of genes that help the immune system recognize which cells belong to the body and which are foreign, like bacteria or viruses. These genes play an important role in immune system function and are involved in autoimmune diseases.
A study conducted between 2019 and 2021 in northwestern Transylvania (Romania) explored the genetic susceptibility of autoimmune thyroid diseases (AITD) by examining the correlations between HLA class II alleles, specifically HLA-DRB1 and HLA-DQB1, in patients with HD and GD compared to a control group. Using molecular biology methods like SSP-PCR and PCR-SSO to analyze DNA samples, the study found that the HLA-DRB103/16 genotype was a susceptibility factor for HD, while the HLA-DRB103 allele, DRB103/16 genotype, and DRB103/DQB106 haplotype increased risk for GD. Additionally, the HLA-DRB113 allele appeared to offer protection against both HD and GD. These findings may help with the prevention and early detection of AITD by identifying specific genetic markers linked to disease development.
CTLA4 (cytotoxic T-lymphocyte antigen-4) is a protein found on T-cells, a type of immune cell. It helps control the immune system by slowing down or stopping T-cells from being too active, preventing them from attacking the body’s own tissues. This is important for keeping the immune system in balance and avoiding autoimmune diseases.
A 2007 study aimed to provide large-scale evidence on whether CTLA4 gene polymorphisms, specifically A49G (rs231775) and CT60 (rs3087243), increase the risk of HD and GD. Meta-analyses were conducted using data from 32 studies for GD 12 studies for HD on A49G, and 15 studies for GD and six for HD on CT60. Group-level data revealed significant associations between the G-allele of both polymorphisms and increased risk for GD and HD, with odds ratios suggesting higher susceptibility for both conditions. The associations were consistent across subjects of Asian and European descent. Additionally, individual-level data showed that the GG-haplotype increased the risk of GD and HD compared to the AA-haplotype. The study concluded that the CT60 polymorphism in CTLA4 is a key genetic factor contributing to the risk of GD and HD in diverse populations.
PTPN22 (protein tyrosine phosphatase non-receptor type 22) is a protein that helps control the immune system by regulating the activity of immune cells. Polymorphisms in its gene can affect how the immune system functions, sometimes leading to autoimmune diseases, where the body mistakenly attacks its own healthy tissues, such as thyroid diseases and type 1 diabetes. A 2011 study identified the minor allele of the SNP rs12730735 to be significantly associated with HD. These findings suggest that PTPN22 gene polymorphisms may contribute to HD risk at least in the Korean population.
Currently, Hashimoto’s disease is not curable. As an autoimmune disorder, once the immune system starts attacking the thyroid, the damage is often permanent. Even though the underlying autoimmune process cannot be reversed, the symptoms of hypothyroidism caused by Hashimoto’s disease can be effectively managed with lifelong hormone replacement therapy. This treatment involves taking synthetic thyroid hormone (levothyroxine) to normalize thyroid hormone levels in the body. Regular monitoring and dosage adjustments are essential to ensure optimal hormone levels and symptom control. While there is no cure for Hashimoto’s, with proper management, most individuals can live normal, healthy lives.
Hashimoto’s disease cannot be fully prevented, as genetics play a significant role in its development. However, certain lifestyle choices and environmental factors might help lower the risk or delay the onset of the disease. Maintaining a balanced diet, managing stress, and avoiding excessive iodine intake can support thyroid health. Since Hashimoto’s disease is an autoimmune condition, limiting exposure to environmental toxins, supporting gut health, and managing chronic inflammation may also help reduce the risk of triggering the disease. Regular monitoring of thyroid function, particularly for individuals with a family history of thyroid issues, can aid early detection and treatment. While prevention isn’t entirely possible, early intervention can minimize the impact of the disease on thyroid function.
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HD is an autoimmune condition where the immune system attacks the thyroid gland, leading to hypothyroidism. It is more common in women and develops gradually, causing symptoms like fatigue, weight gain, and depression. While not curable, it can be managed with synthetic thyroid hormones. Hashimoto’s is often studied alongside GD, another autoimmune thyroid condition that leads to hyperthyroidism. Genetic factors, such as polymorphisms in the CTLA4 and PTPN22 genes, have been linked to an increased risk of HD. Research has identified specific gene variants, including certain HLA-alleles, that influence susceptibility to both HD and GD. Prevention of Hashimoto’s is not fully possible due to its strong genetic component, but lifestyle changes may help reduce risk or delay onset.
