Hashimoto’s disease is an autoimmune condition that can gradually affect thyroid hormone production.

Hashimoto's disease, also called Hashimoto's thyroiditis, is an autoimmune condition in which the immune system mistakenly targets the thyroid gland. Over time, inflammation can damage the gland and reduce its ability to make enough thyroid hormones. Many people eventually develop hypothyroidism (an underactive thyroid), although some have normal thyroid hormone levels for years.

Hashimoto's disease can develop gradually, and symptoms are not always obvious at first. Fatigue, feeling unusually cold, constipation, dry skin, hair thinning and unexplained weight gain can occur when thyroid hormone levels become low—but these symptoms can also have other causes. Blood tests, rather than symptoms alone, help establish what is happening.

What Is Hashimoto's Disease?

The thyroid is a small, butterfly-shaped gland at the front of the neck. It produces hormones—mainly thyroxine (T4) and triiodothyronine (T3)—that help regulate energy use, body temperature, heart rate, digestion and other functions.

In Hashimoto's thyroiditis, immune cells and thyroid antibodies contribute to inflammation of the gland. The most commonly measured antibodies are thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb). Over time, the thyroid may become enlarged (a goitre) or lose hormone-producing capacity. The pace varies: some people remain biochemically euthyroid (normal thyroid function) while others develop hypothyroidism.

Hashimoto's Disease at a Glance

12 Possible Symptoms of Hashimoto's Disease

Many people have no symptoms in the early stages. Symptoms usually develop when thyroid hormone production becomes insufficient. They may appear gradually and overlap with other conditions, so they cannot confirm Hashimoto's on their own.

1. Persistent Fatigue

Feeling unusually tired, sluggish or low in energy is common in hypothyroidism. Fatigue is nonspecific and can also be related to sleep problems, anaemia, stress, infection or other health conditions.

2. Increased Sensitivity to Cold

People with low thyroid hormone levels may feel colder than others in the same environment because thyroid hormones influence heat production and energy use.

3. Unexplained Weight Gain

Hypothyroidism can contribute to modest weight gain, partly through changes in metabolism and fluid balance. Significant or rapid weight changes should not automatically be attributed to the thyroid.

4. Constipation

Reduced thyroid activity can slow digestive movement, making bowel movements less frequent or more difficult.

5. Dry Skin and Hair Changes

Skin may become dry or rough, and hair may become dry, coarse or thinner. Hair loss has many possible causes, including iron deficiency and hormonal changes.

6. Muscle Aches or Joint Stiffness

Some people experience muscle cramps, aches, weakness or joint discomfort when thyroid hormone levels are low.

7. Low Mood or Difficulty Concentrating

Hypothyroidism can be associated with low mood, slowed thinking or difficulty concentrating. These symptoms deserve a broad assessment rather than assuming they are caused by thyroid disease alone.

8. Heavy or Irregular Menstrual Periods

Thyroid hormone changes can affect menstrual patterns and may contribute to heavier, irregular periods or fertility difficulties in some people.

9. Slower Heart Rate

Low thyroid hormone levels can slow the heart rate. A very slow pulse, fainting, chest discomfort or breathlessness needs medical assessment.

10. Puffy Face or Swelling

Some people with more significant hypothyroidism develop puffiness around the face or eyes, or swelling in other areas.

11. Neck Fullness or Goitre

The thyroid may enlarge and create a visible swelling or a feeling of fullness at the front of the neck. A new or growing neck lump should be examined.

12. Changes in Children and Adolescents

In children, untreated hypothyroidism may affect growth, development, school performance or puberty. A child with possible thyroid symptoms needs assessment by a paediatric clinician.

What Causes Hashimoto's Disease?

The exact trigger is not fully understood. Hashimoto's is thought to arise from a combination of genetic susceptibility and environmental or biological factors. It is not caused by a personal failure, and it is not contagious.

• Genetic and family factors: Thyroid or other autoimmune conditions may occur more often in some families.
• Sex and age: Hashimoto's is diagnosed more often in women and becomes more common with age, but it can affect people of any sex and age, including children.
• Other autoimmune conditions: Having another autoimmune disorder may increase the likelihood of thyroid autoimmunity.
• Environmental and medical factors: Some infections, medicines or exposures may be relevant in certain people, but they do not explain every case.
• Iodine exposure: Excessive iodine intake can affect thyroid function and may aggravate autoimmune thyroid problems in susceptible people. This does not mean everyone should avoid normal dietary iodine.

Who May Have a Higher Risk?

How Is Hashimoto's Disease Diagnosed?

A clinician considers symptoms, medical and family history, examination of the neck and blood test results. No single symptom or antibody result should be interpreted in isolation.

1. TSH Test

Thyroid-stimulating hormone (TSH) is produced by the pituitary gland and signals the thyroid to make hormones. A high TSH often suggests that the thyroid is not producing enough hormone, although interpretation depends on the laboratory range, age, pregnancy status, medicines and clinical context.

2. Free T4 Test

Free T4 measures the unbound portion of thyroxine in the blood. High TSH with low free T4 commonly indicates overt primary hypothyroidism. High TSH with free T4 in the reference range may indicate subclinical hypothyroidism.

3. TPO Antibody Test

Thyroid peroxidase antibodies are commonly present in Hashimoto's disease. A positive result can support an autoimmune cause, especially when thyroid function tests are abnormal. However, positive antibodies can also occur in people whose thyroid hormone levels are normal.

4. Thyroglobulin Antibodies

Thyroglobulin antibodies may be measured in selected cases. TPO antibodies are generally the primary antibody test used to support the diagnosis.

5. Thyroid Ultrasound

An ultrasound is not required for everyone. It may be considered if the thyroid is enlarged, a nodule or lump is felt, or the diagnosis remains uncertain. Ultrasound can show gland size and tissue appearance but does not replace blood tests for thyroid function.

Hashimoto's Disease vs Hypothyroidism: What Is the Difference?

These terms are related but do not mean exactly the same thing. Hashimoto's is an autoimmune disease that can damage the thyroid. Hypothyroidism describes a state in which the thyroid does not produce enough hormone. Hashimoto's is a common cause of hypothyroidism, but hypothyroidism can also result from thyroid surgery, radioactive iodine treatment, certain medicines or other conditions.

How Is Hashimoto's Disease Treated?

Treatment depends on thyroid function, symptoms, age, pregnancy status and other health factors. The aim is to maintain appropriate thyroid hormone levels and manage any associated problems—not to chase antibody numbers.

When Thyroid Hormone Levels Are Normal

If TPO antibodies are positive but TSH and free T4 are normal, thyroid hormone medication is usually not required solely because antibodies are present. A clinician may monitor TSH over time, particularly if symptoms develop, pregnancy is planned or other risk factors exist.

When Hypothyroidism Develops

Levothyroxine is the standard thyroid hormone replacement for hypothyroidism due to Hashimoto's. It is a synthetic form of T4, the same hormone the thyroid naturally produces. The dose is individualised using factors such as body size, age, heart health, pregnancy status and laboratory results.

How to Take Levothyroxine Correctly

• Take it exactly as prescribed, consistently at the same time each day.
• Many people take it with water on an empty stomach, usually 30–60 minutes before breakfast; follow the specific instructions from your clinician or pharmacist.
• Calcium and iron supplements can reduce absorption. They are commonly separated from levothyroxine by about four hours, but confirm the timing with your care team.
• Coffee, food, soy and some medicines may affect absorption in some circumstances. Consistency and clinician guidance are important.
• Do not increase, reduce or stop the dose yourself.

TSH is commonly rechecked around 6–8 weeks after starting treatment or changing the dose, with later testing once levels are stable. The exact schedule is individualised. Many people with established Hashimoto-related hypothyroidism need long-term, often lifelong, replacement therapy.

Can Hashimoto's Disease Be Cured?

There is currently no established treatment that permanently removes the autoimmune process. However, when Hashimoto's causes hypothyroidism, levothyroxine can replace the hormone the thyroid is no longer making and usually controls the hormone deficiency effectively. People can often live full, active lives with appropriate treatment and follow-up.

If thyroid function is still normal, medication may not be needed. Monitoring is important because thyroid function can change over time.

Diet and Nutrition: What Should You Eat?

No specific diet has been proven to cure Hashimoto's or reliably switch off thyroid autoimmunity. A balanced eating pattern can support general health and help prevent nutritional deficiencies, but it does not replace thyroid hormone treatment when that treatment is indicated.

Practical Nutrition Guidance

• Use normal dietary iodine, not megadoses: Iodine is essential for thyroid hormone production, but excess iodine from kelp, seaweed concentrates or high-dose supplements can worsen thyroid dysfunction in susceptible people. Do not start iodine supplements without medical advice.
• Include varied protein sources: Pulses, dairy, eggs, fish, poultry, soy foods, nuts and seeds can contribute protein according to dietary preference.
• Meet selenium needs through food: Selenium is found in foods such as fish, eggs, meat, cereals and some nuts. High-dose selenium supplements are not routinely recommended for everyone with Hashimoto's; discuss them with a clinician.
• Check iron, B12 or vitamin D only when appropriate: Deficiencies can contribute to fatigue or other symptoms, but supplements should be based on dietary assessment, risk factors or test results.
• Do not eliminate gluten automatically: A gluten-free diet is necessary for coeliac disease, but it is not a proven universal treatment for Hashimoto's. People with symptoms or risk factors should discuss coeliac testing before removing gluten, because a gluten-free diet can affect test accuracy.
• Choose a sustainable balanced pattern: Vegetables, fruit, whole grains, pulses, healthy fats and appropriate protein portions support overall health.

Hashimoto's Disease and Pregnancy

Thyroid hormones are important before conception and throughout pregnancy. People with known Hashimoto's or hypothyroidism who are planning pregnancy should discuss thyroid tests and medication with their clinician in advance. Thyroid hormone requirements often increase during pregnancy, so monitoring and dose adjustment may be needed.

Do not change levothyroxine doses on your own unless you have a specific pre-agreed plan from your treating clinician. Pregnancy-specific TSH reference ranges and treatment decisions differ from those used in non-pregnant adults. Antibody positivity with normal thyroid function does not automatically mean levothyroxine is required; current pregnancy guidance recommends an individualised approach.

After delivery, thyroid function may change. Follow-up testing is important, especially if medication was adjusted during pregnancy or symptoms develop.

Possible Complications If Hypothyroidism Is Untreated

Not everyone with Hashimoto's develops complications. However, persistent untreated hypothyroidism can contribute to:

• Raised cholesterol and increased cardiovascular risk.
• Menstrual irregularity and fertility difficulties.
• Pregnancy-related complications if thyroid hormone deficiency is not appropriately managed.
• Goitre or enlargement of the thyroid in some people.
• Rarely, severe hypothyroidism can progress to myxoedema crisis, a life-threatening emergency.

When to Seek Medical Help

Arrange a routine medical appointment if you have persistent symptoms such as fatigue, cold intolerance, constipation, unexplained weight change, hair thinning or neck fullness—especially if you have a family history of thyroid disease or another autoimmune condition.

A rapidly enlarging neck swelling, difficulty swallowing or breathing, or a new firm neck lump also needs prompt clinical assessment.

Long-Term Monitoring and Daily Living

• Attend thyroid blood tests at the intervals recommended by your clinician.
• Use levothyroxine consistently if prescribed and tell your clinician about missed doses or new medicines.
• Do not repeatedly measure thyroid antibody levels to judge whether treatment is working; TSH and free T4 are generally more useful for monitoring thyroid function.
• Tell your clinician if you are planning pregnancy, become pregnant or are breastfeeding.
• Discuss persistent symptoms even when TSH is in range; other causes may need assessment rather than simply increasing thyroid medication.
• Keep a list of medicines and supplements, including calcium, iron, antacids and biotin-containing products. Biotin can interfere with some thyroid blood test methods; ask the laboratory or clinician whether and when to pause it before testing.

Frequently Asked Questions About Hashimoto's Disease

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Trusted Medical Sources and Further Reading

• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): Hashimoto's Disease — symptoms, causes, diagnosis, treatment and complications.
• American Thyroid Association: Hashimoto's Thyroiditis — antibody testing, monitoring and when levothyroxine is used.
• NIDDK: Hypothyroidism — treatment, medicine timing and iodine considerations.
• Mayo Clinic: Hashimoto's Disease—Diagnosis and Treatment — TSH, T4 testing and clinical evaluation.
• American Thyroid Association: Hypothyroidism in Pregnancy — thyroid management before and during pregnancy.
• Systematic Review and Meta-analysis: Selenium Supplementation in Hashimoto Thyroiditis — evidence and limitations of supplementation studies.
• American Thyroid Association 2026 Guidelines: Thyroid Disease in Preconception, Pregnancy and Postpartum — current pregnancy-specific recommendations.

Conclusion: Understanding Hashimoto's Disease

Hashimoto's disease is a common autoimmune thyroid condition that may gradually reduce the thyroid's ability to produce hormones. Some people have positive thyroid antibodies but normal hormone levels, while others develop hypothyroidism and need levothyroxine.

The most useful approach is an accurate diagnosis, thyroid function monitoring, medicine when clinically indicated and a balanced diet without unnecessary high-dose supplements or restrictive rules. If you notice persistent symptoms or are planning a pregnancy, discuss thyroid testing with a qualified healthcare professional.

Medical disclaimer: This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Do not start, stop or change levothyroxine, iodine, selenium or other supplements without discussing them with your healthcare professional. Pregnancy and childhood thyroid conditions require individual clinical assessment.