Hashimoto's disease

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Hashimoto's disease is a condition that affects the function of the thyroid, which is a butterfly-shaped gland in the lower neck. The thyroid makes hormones that help regulate a wide variety of critical body functions. For example, thyroid hormones influence growth and development, body temperature, heart rate, menstrual cycles, and weight. Hashimoto's disease is a form of chronic inflammation that can damage the thyroid, reducing its ability to produce hormones.

One of the first signs of Hashimoto's disease is an enlargement of the thyroid called a goiter. Depending on its size, the enlarged thyroid can cause the neck to look swollen and may interfere with breathing and swallowing. As damage to the thyroid continues, the gland can shrink over a period of years and the goiter may eventually disappear.

Other signs and symptoms resulting from an underactive thyroid can include excessive tiredness (fatigue), weight gain or difficulty losing weight, hair that is thin and dry, a slow heart rate, joint or muscle pain, and constipation. People with Hashimoto's disease may also have a pale, puffy face and feel cold even when others around them are warm. Affected women can have heavy or irregular menstrual periods and difficulty conceiving a child (impaired fertility). Difficulty concentrating and depression can also be signs of a shortage of thyroid hormones.

Hashimoto's disease usually appears in mid-adulthood, although it can occur earlier or later in life. Its signs and symptoms tend to develop gradually over months or years.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Hashimoto's disease is thought to result from a combination of genetic and environmental factors. Some of these factors have been identified, but many remain unknown.

Hashimoto's disease is classified as an autoimmune disorder, one of a large group of conditions that occur when the immune system attacks the body's own tissues and organs. In people with Hashimoto's disease, white blood cells called lymphocytes accumulate abnormally in the thyroid, which can damage it. The lymphocytes make immune system proteins called antibodies that attack and destroy thyroid cells. When too many thyroid cells become damaged or die, the thyroid can no longer make enough hormones to regulate body functions. This shortage of thyroid hormones underlies the signs and symptoms of Hashimoto's disease. However, some people with thyroid antibodies never develop hypothyroidism or experience any related signs or symptoms.

People with Hashimoto's disease have an increased risk of developing other autoimmune disorders, including vitiligo, rheumatoid arthritis, Addison disease, type 1 diabetes, multiple sclerosis, and pernicious anemia.

Variations in several genes have been studied as possible risk factors for Hashimoto's disease. Some of these genes are part of a family called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). Other genes that have been associated with Hashimoto's disease help regulate the immune system or are involved in normal thyroid function. Most of the genetic variations that have been discovered are thought to have a small impact on a person's overall risk of developing this condition.

Other, nongenetic factors also play a role in Hashimoto's disease. These factors may trigger the condition in people who are at risk, although the mechanism is unclear. Potential triggers include changes in sex hormones (particularly in women), viral infections, certain medications, exposure to ionizing radiation, eating large amounts of foods that contain animal proteins, and excess consumption of iodine (a substance involved in thyroid hormone production).

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

The inheritance pattern of Hashimoto's disease is unclear because many genetic and environmental factors appear to be involved. However, the condition can cluster in families, and having a close relative with Hashimoto's disease or another autoimmune disorder likely increases a person's risk of developing the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Hashimoto's disease affects 1 to 2 percent of people in the United States. It occurs more often in women than in men, which may be related to hormonal factors. Hashimoto's disease is the most common cause of thyroid underactivity (hypothyroidism) in the United States.

Which doctor should you see?

The suggested department for discussing Hashimoto's disease is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Hashimoto's disease. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.