What is it?
Hashimoto’s thyroiditis is an autoimmune condition. It is also called chronic lymphocytic thyroiditis. Antibodies, either thyroid peroxidase (TPO) antibodies and/or anti-thyroglobulin (Tg) antibodies damage the thyroid gland. Over time the inflammation can lead to enlargement of the thyroid gland or hypothyroidism.
In fact, Hashimoto’s thyroiditis is the most common cause of hypothyroidism. About 5% of the population develop hypothyroidism at some stage in their lifetime and Hashimoto’s thyroiditis is the cause of hypothyroidism in two out of every three patients.
Hashimoto’s thyroiditis was first described by a Japanese doctor, Hakura Hashimoto, in 1912.
The TPO and Tg antibodies are thought to develop following T cell–mediated destruction of the thyroid gland.
Who gets Hashimoto’s thyroiditis?
Like most autoimmune conditions, Hashimoto’s thyroiditis is more common in women. The typical patient is a 30–50-year-old woman, although it can occur in males and in any age group, including children. Hashimoto’s thyroiditis often runs in families, and there is an increased incidence of Hashimoto’s thyroiditis in patients with Down Syndrome.
How is it diagnosed?
Hashimoto’s thyroiditis presents in several different ways. It most commonly presents as a mildly enlarged thyroid gland and hypothyroidism. It may present with a markedly enlarged thyroid gland, euthyroidism or even thyrotoxicosis (a condition called Hashitoxicosis) in the early stage of the disease.
It is suspected clinically and confirmed with positive thyroid peroxidase (TPO) antibodies and/or anti-thyroglobulin (Tg) antibodies.
Hashimoto’s thyroiditis on ultrasound presents with a diffusely enlarged gland in the early stage or a small atrophic gland in the later stages. It is characterised by hypoechoic (dark) heterogeneous thyroid parenchyma with fibrous echogenic (white) bands. Small nodules about 1–7mm in size and increased vascularity on Doppler is seen. Sometimes the nodules are larger, measuring 15–18mm. A giraffe pattern with dark nodules and pale fibrous bands mimics the appearance of giraffe skin and is characteristic of Hashimoto’s thyroiditis.
Sometimes Hashimoto’s thyroiditis is only diagnosed by a pathologist after thyroidectomy.
In summary, Hashimoto’s thyroiditis is diagnosed in the following ways:
- Large thyroid
- Hypothyroidism
- Positive TPO or Tg antibodies
- Characteristic ultrasound features
- Pathological diagnosis following thyroidectomy.
What is the prognostic significance of positive TPO antibodies?
About 50% of patients with positive TPO antibodies eventually develop hypothyroidism. It is for this reason that it is recommended to perform annual thyroid function tests (TSH, fT4) in patients with positive TPO antibodies.
TPO and Tg antibodies precede the development of hypothyroidism by three to seven years. TPO and Tg antibodies are the earliest footprint of Hashimoto’s thyroiditis.
About 10% of patients with Hashimoto’s thyroiditis have negative TPO antibodies.
There is an 80-fold increase in the development of thyroid lymphoma in patients with Hashimoto’s thyroiditis.
The treatment of Hashimoto’s thyroiditis
Thyroxine therapy is the mainstay of treatment for patients with Hashimoto’s thyroiditis who develop hypothyroidism.
Controversies in Hashimoto’s thyroiditis
Vitamin D deficiency and micronutrient deficiencies, especially selenium deficiency, have been implicated in the development of Hashimoto’s thyroiditis. There is a literature on hypothyroidism symptoms in euthyroid patients with thyroiditis. There is also a literature on persistent hypothyroidism symptoms in patients treated with levothyroxine who are biochemically euthyroid.
Summary
Hashimoto’s thyroiditis is the leading cause of hypothyroidism and is suspected when thyroperoxidase antibodies are positive. Euthyroid patients with positive TPO antibodies should have annual thyroid function tests as a high proportion of these patients become hypothyroid with time.
References:
- Francis Hall. Understanding thyroiditis. GP Voice. 2024 Nov; 25–27.
- Ragusa F, Fallahi P, Elia G, et al. Hashimoto’s thyroiditis: Epidemiology, pathogenesis, clinic and therapy. Best Practice & Research Clinical Endocrinology & Metabolism. 2019; 33:6: 101367.
- Zhang H, Tong W, Zeng W, et al. Persistent symptoms in euthyroid Hashimoto’s thyroiditis: current hypotheses and emerging management strategies. Front. Endocrinol. 2025;16:1627787.