# Hashimoto’s Thyroiditis

URL: https://thethyroidologist.com/conditions/hashimotos-thyroiditis/
Section: Conditions
Last medically reviewed: 2025-11-01

> Hashimoto’s thyroiditis — the most common cause of hypothyroidism. What it is, how anti-TPO testing works, symptoms, and treatment with levothyroxine.

Hashimoto’s thyroiditis is an autoimmune disease in which the immune system attacks the thyroid gland, gradually reducing its ability to produce hormone. It is the most common cause of hypothyroidism in iodine-sufficient countries.
Despite its progressive nature, it is very manageable once diagnosed.

## What is happening in the gland?

In Hashimoto’s, lymphocytes infiltrate the thyroid and produce antibodies — most commonly anti-TPO (anti-thyroid peroxidase) and sometimes anti-thyroglobulin antibodies. Over years this causes inflammation and fibrosis, shrinking hormone output.
The condition has a genetic component and clusters with other autoimmune diseases such as type 1 diabetes, coeliac disease, rheumatoid arthritis and vitiligo.

## Symptoms and course

Early on, patients may be entirely asymptomatic, or have a mildly enlarged gland (goitre). As hormone production falls, typical hypothyroid symptoms appear: fatigue, weight gain, cold intolerance, constipation and low mood. A small subset may pass through a temporary hyperthyroid phase as stored hormone leaks from the inflamed gland.
The progression is usually slow — often over years — which is why symptoms can be subtle and attributed to other causes.

## Diagnosis and treatment

Diagnosis combines TSH and free T4 testing with anti-TPO antibody measurement. A positive anti-TPO result confirms the autoimmune mechanism even when hormone levels are still normal (a state sometimes called euthyroid autoimmune thyroiditis).
Treatment is levothyroxine once hypothyroidism develops; there is no treatment that stops the autoimmune process itself. Patients with normal function but positive antibodies are monitored periodically, particularly during pregnancy.

## Frequently asked questions

### Can Hashimoto’s be reversed?

The autoimmune process itself cannot currently be reversed, but the resulting hypothyroidism is fully treatable with levothyroxine. Most patients on adequate replacement live normal, healthy lives.

### Does a goitre mean I have Hashimoto’s?

Not necessarily. A goitre has many causes — iodine deficiency, nodules, Graves’ disease, thyroiditis. Ultrasound and antibody testing help clarify the cause.

### Should family members be tested?

If you have Hashimoto’s, first-degree relatives have a somewhat higher risk of thyroid autoimmunity. Discuss screening with your doctor, especially if they have symptoms.

## Disclaimer

The content on this website is for general educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about your specific condition.

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