Last reviewed: May 12, 2026 Last updated: May 12, 2026

Written by: Jay Hastings , CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance. His work has included scaling healthcare startups, leading CLIA lab integrations, and helping expand consumer access to precision health tools.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

TSHR and Thyroid Health: What Your rs3783938 Genotype Means

The thyroid gland plays a central role in metabolism, energy, and hormone balance. It influences how the body uses energy, regulates temperature, supports healthy hair and skin, and interacts with reproductive hormones. The TSHR gene encodes the thyroid stimulating hormone receptor, a protein on thyroid cells that responds to TSH from the pituitary. Variations in TSHR can alter immune regulation in the thyroid and influence risk for autoimmune thyroid conditions such as Hashimoto's thyroiditis.

About rs3783938

rs3783938 is a single nucleotide variant in the TSHR gene. One version of this variant, called the T allele, is associated with an increased risk of autoimmune thyroid disease. Your genotype at rs3783938 can help indicate relative risk for Hashimoto's thyroiditis, but it does not determine whether you will develop disease. Genes interact with diet, environment, stress, infections, and other factors.

Two effect alleles (TT): higher genetic risk

Having two copies of the T allele (TT) is associated with a higher risk of developing Hashimoto's thyroiditis, an autoimmune form of hypothyroidism where immune cells attack thyroid tissue. If autoimmune damage develops, symptoms can include persistent fatigue, increased sensitivity to cold, unexplained weight gain, constipation, dry or thinning hair, and changes in mood or memory. Not everyone with TT will develop disease, but awareness supports proactive monitoring and lifestyle steps to reduce modifiable risk factors.

  • Be vigilant for symptoms listed above and discuss any changes with your healthcare provider.
  • Consider baseline and periodic thyroid testing: TSH, free T4, free T3, and thyroid peroxidase and thyroglobulin antibodies.
  • Optimize nutrients that support thyroid function and immune balance, including selenium, zinc, vitamin D, vitamin A, and moderate iodine.
  • Adopt an anti-inflammatory eating pattern and manage stress, sleep, and toxin exposure to help reduce autoimmune activation.
One effect allele (CT): increased genetic risk

Carrying one T allele (CT) is associated with an elevated risk for Hashimoto's thyroiditis compared to individuals without the T allele, roughly around 1.4 times higher. This genotype does not guarantee disease, but it suggests a slightly increased susceptibility to autoimmune thyroid dysfunction. The same symptoms and preventive strategies apply as for other genotypes, with emphasis on monitoring and modifiable lifestyle factors.

  • Watch for early symptoms and notify your healthcare provider if they appear.
  • Request periodic thyroid screening: TSH with reflex to free T4 and, when indicated, thyroid antibodies.
  • Support thyroid and immune health through nutrient-rich diet, adequate vitamin D, and careful iodine intake.
  • Reduce inflammation with Mediterranean-style eating, regular sleep, stress reduction, and avoiding known environmental thyroid disruptors.
Zero effect alleles (CC): typical or lower genetic risk

Having two copies of the non-effect C allele (CC) is associated with a typical or lower genetic risk for Hashimoto's thyroiditis relative to carriers of the T allele. This does not mean you cannot develop thyroid disease. Environmental factors, infections, nutrient deficiencies, and other genes also influence risk. Maintaining thyroid-supporting habits remains valuable for overall health and prevention.

  • Continue routine thyroid monitoring as part of preventive care or when symptoms arise.
  • Maintain a balanced intake of selenium, zinc, iodine, vitamin D, and vitamin A for ongoing thyroid support.
  • Practice an anti-inflammatory lifestyle to reduce the likelihood of immune dysregulation.

Common Signs of Thyroid Dysfunction

  • Fatigue and low energy
  • Increased sensitivity to cold
  • Unexplained weight gain or difficulty losing weight
  • Constipation
  • Dry, thinning hair or hair loss
  • Irregular menstrual cycles or changes in fertility
  • Low mood, brain fog, or slowed thinking

Nutrition and Supplements to Support Thyroid Health

These recommendations support thyroid function and immune balance. Personal needs vary, so review supplements and doses with your healthcare provider.

  • Selenium: Important for antioxidant enzymes in the thyroid and for converting thyroid hormones. Foods: Brazil nuts (small amounts), seafood, poultry, eggs, and whole grains.
  • Zinc: Supports hormone synthesis and immune function. Foods: oysters, beef, pumpkin seeds, lentils, and chickpeas.
  • Iodine: Required for thyroid hormone production. Use moderate intake only. Excessive iodine can trigger or worsen autoimmune thyroid disease. Food sources: iodized salt, seaweed, dairy, and seafood. Discuss targeted needs with your clinician before supplementing.
  • Vitamin D: Low vitamin D is common and linked with autoimmunity. Safe sun exposure and testing guided supplementation can help maintain adequate levels.
  • Vitamin A: Supports thyroid hormone action and immune health. Focus on dietary sources such as liver in moderation, orange and dark green vegetables, and dairy. Avoid high dose vitamin A supplements without medical supervision.
  • Anti-inflammatory diet: A Mediterranean-style eating pattern with plenty of vegetables, fruits, fatty fish, olive oil, nuts, seeds, legumes, and whole grains supports immune regulation and metabolic health.

Lifestyle and Environmental Considerations

  • Stress management: Chronic stress can dysregulate immune function. Practices such as mindfulness, gentle movement, breathwork, and counseling can be helpful.
  • Sleep: Aim for consistent, restorative sleep to support hormone balance and immune resilience.
  • Environmental toxins: Minimize exposure to endocrine disrupting chemicals such as BPA, certain flame retardants, and pesticides. Use glass or stainless steel, filter drinking water when possible, and choose low-toxin household products.
  • Infections and smoking: Past infections and smoking can impact autoimmune risk. Avoid tobacco and address persistent infections with medical care.
  • Body weight and activity: Maintain a healthy weight through regular physical activity and balanced nutrition. Exercise supports metabolism and immune health.

Recommended Medical Tests and Monitoring

  • TSH: First-line screening for thyroid function.
  • Free T4 and free T3: Assess circulating active thyroid hormones when TSH is abnormal or symptoms are present.
  • Thyroid antibodies: Anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin antibodies can help identify autoimmune thyroid disease.
  • Vitamin D 25-Hydroxy: Evaluate and correct deficiency.
  • Selenium and zinc status: Test when deficiency is suspected or before long-term supplementation at high doses.

When to See a Healthcare Provider

  • If you notice persistent symptoms such as fatigue, weight changes, cold sensitivity, hair loss, or menstrual or fertility changes.
  • If you have a family history of autoimmune thyroid disease or other autoimmune conditions.
  • Before starting supplements that affect thyroid function or immune activity, especially iodine or high dose vitamin A.
  • For individualized testing and interpretation of results in the context of your health history and medications.

PlexusDx provides educational information about genetic predispositions and health. This content is not medical advice. Always consult your healthcare provider to interpret test results, diagnose conditions, and make treatment decisions tailored to your personal health needs.

If this genetic variant is present in your PlexusDx results, the following tests and reports are commonly used to explore it further:

🧬 Genetic Tests:

🧪 Blood Tests:

📄 Genetic Report:

Frequently Asked Questions About Thyroid and TSHR rs3783938

What does the TSHR rs3783938 genotype mean for my risk of Hashimoto’s thyroiditis?

The rs3783938 variant is in the TSHR gene, which encodes the thyroid stimulating hormone receptor involved in thyroid signaling and immune regulation. Having the T allele is associated with increased genetic risk of autoimmune thyroid disease, especially Hashimoto’s thyroiditis. However, your genotype cannot determine whether you will develop disease—risk is influenced by genes interacting with diet, environment, stress, infections, and other factors.

How do TT, CT, and CC rs3783938 genotypes differ in thyroid autoimmunity risk?

TT (two T alleles) is associated with higher genetic risk for Hashimoto’s thyroiditis. CT (one T allele) is associated with an elevated risk compared with people without the T allele (reported roughly around 1.4x higher). CC (two C alleles) is associated with typical or lower genetic risk, though thyroid disease can still occur due to non-genetic factors and other genes.

What thyroid tests and lifestyle steps are recommended if I have the rs3783938 T allele?

For monitoring, clinicians commonly use TSH as the first-line test, with reflex testing to free T4/free T3 when indicated, plus thyroid antibodies (anti-TPO and anti-thyroglobulin) to assess autoimmunity. Lifestyle and nutrition steps that support thyroid function and immune balance include an anti-inflammatory, Mediterranean-style eating pattern; adequate but not excessive iodine intake; and nutrients such as selenium, zinc, vitamin D, and vitamin A. Manage stress, prioritize restorative sleep, minimize exposure to endocrine-disrupting toxins (e.g., BPA and certain pesticides), and avoid smoking. Always review supplements—especially iodine and high-dose vitamin A—with your healthcare provider.

What tests can help me learn more about Thyroid and TSHR rs3783938?

The Hormone, Thyroid, and Reproductive Health Genetic Test delivers over 85 personalized genetic insights through a comprehensive Hormone & Fertility Genetic Report, explaining inherited tendencies related to hormonal balance, reproductive function, and endocrine signaling. The Mens Hormone and Fertility Health Genetic Report translates your results into personalized, actionable guidance. Your healthcare provider can also recommend targeted blood tests based on your specific pathway results and health history to complement your genetic insights with current biomarker data.

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance. References are included at the end of the article when scientific, medical, or health-related claims are discussed.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.