Key learning points
- Hashimoto’s thyroiditis is the most common form of thyroiditis.
- Subacute or De Quervain’s thyroiditis is most likely due to a viral infection
- Thyroiditis can often lead to hypothyroidism developing
- Amiodarone can cause hyperthyroidism or hypothyroidism
- An enlarging or hard thyroid could also be due to a carcinoma
Inflammation of the thyroid gland (thyroiditis) comprises many common disorders of the thyroid gland. Thyroiditis affects mainly women and can occur at any age. Affected patients can be euthyroid, hypothyroid or hyperthyroid depending on the cause. Many patients ultimately develop permanent hypothyroidism.
Classification of thyroiditis
- Hashimoto’s (chronic lymphocytic/autoimmune)
- De Quervain’s (painful subacute)
- Painless postpartum
- Painless sporadic
- Drug-induced
- Riedel’s
- Suppurative
Hashimoto’s thyroiditis
Hashimoto’s thyroiditis is the most common form of thyroiditis. It is a form of autoimmune thyroditis; more common in women and in late middle age. Thyroid peroxidase (TPO) antibodies are usually present in this condition, often in very high levels. It may be associated with other endocrine organ deficiencies such as diabetes mellitus or Addison's disease. Hashimoto’s thyroiditis also occurs more commonly in patients with Down’s and Turner’s syndromes.
It produces atrophic changes with regeneration. This can lead to a goitre forming. Patients with Hashimoto’s thyroiditis are usually hypothyroid or euthyroid. However, they may have an initial thyrotoxic phase at presentation.
Specific helper-T lymphocytes are activated in this condition which results in an immune response directed against the thyroid cell. This activation may be triggered by a viral infection.
Although thyroid lymphoma is rare, the risk of thyroid lymphoma is increased 60-fold in patients with Hashimoto’s thyroiditis1. Patients presenting with a new thyroid lump should undergo fine-needle aspiration biopsy.
Figure 1: A woman presenting with an enlarged thyroid who has Hashimoto's thyroiditis.
Video 1: A video of the histology of Hashimotos thyroiditis.
Iodine insufficiency
Hashimoto’s thyroiditis and postpartum thyroiditis are characterized by antibodies against thyroid peroxidase and thyroglobulin. The geographical variations in the incidence of Hashimoto’s thyroiditis, postpartum thyroiditis and sporadic thyroiditis suggest that dietary insufficiency of iodine may protect against autoimmune thyroiditis. HLA-DR3, HLA-DR4 and HLA-DR5 have been associated with Hashimoto’s thyroiditis and painless thyroiditis in Caucasians. There is some evidence linking cytotoxic T lymphocytes with familial Hashimoto’s thyroiditis.
Subacute thyroiditis (De Quervain’s thyroiditis)
Subacute thyroiditis is also known as De Quervain’s thyroiditis or granulomatous thyroiditis. It is most common in women between 20 and 50 years old.
It is an acute inflammatory disorder of the thyroid gland most likely due to viral infection. The mumps virus, coxsackievirus and adenoviruses have been implicated. This can lead to a moderate enlargement of the thyroid gland. It leads to a transient hyperthyroidism. Hypothyroidism, usually transient, often then follows after a few weeks from initial presentation.
Figure 2: A histological specimen of a patient who had De Quervain’s thyroiditis.
Fever, malaise and soreness in the neck are the main features. Patients may present with painful swelling of one or both of their thyroid lobes. The erythrocyte sedimentation rate (ESR) is markedly raised (>100 mm/hour) and thyroid autoantibodies are usually not detectable.
Subacute thyroiditis can be distinguished from Graves’ disease by the low uptake of tracer on a thyroid uptake scan (there is increased uptake in Graves’ disease).
Thyroid function resolves spontaneously in >95% of patients, but painful subacute thyroiditis can recur in <2% of patients. Patients usually are given symptomatic relief with non-steroidal anti-inflammatories. Rarely, corticosteroids are useful for severe thyroid pain. Beta blockers may help to control thyrotoxicosis symptoms. If hypothyroidism occurs then thyroxine replacement therapy is required.
It is usually a self-limiting condition with spontaneous recovery.
Painless postpartum thyroiditis
This is a form of painless thyroiditis occurring in women in the first year after delivery. Patients may be hyperthyroid or hypothyroid. The cause is unclear, but may be due to the immune recovery in the postpartum period that follows relative immune suppression during pregnancy.
Initially, there is a thyrotoxic phase that may last for up to two months; this is followed by a phase of hypothyroidism for approximately 6–8 months. A large proportion of women recover with normal thyroid function, but there are some who develop hyperthyroidiam. Some studies have found a link between postpartum thyroiditis and post-natal depression.
Initially patients usually have a small, firm and non-tender goitre, with high concentrations of thyroid peroxidase antibodies and thyroglobulin antibodies. Their erythrocyte sedimentation rate is normal.
Medical treatment is not usually needed as it is usually a self-limiting condition.
Painless sporadic thyroiditis
This condition is similar to postpartum thyroiditis other than it does not occur after pregnancy.
Painless sporadic thyroiditis is uncommon. It is due to lymphocytic infiltration and the clinical course is similar to painless postpartum thyroiditis. There is usually a high concentration of antibodies against thyroid peroxidase. Beta-blockers are sometimes given for symptomatic relief.
Drug-induced thyroiditis
Many medications and certain cytokines affect thyroid function and cause thyroiditis.
Amiodarone may cause hypothyroidism in approximately 20% of patients who have thyroid autoimmunity. Amiodarone can also lead to thyrotoxicosis in some patients2.
Lithium can cause thyrotoxicosis after long-term use. This may be due to the direct toxic effects on thyroid cells.
Therapy using interferon-α and interleukin-2 has been implicated in destructive inflammatory thyroiditis.
Riedel’s thyroiditis
Riedel’s thyroiditis is a very rare chronic inflammatory disorder that leads to progressive fibrosis of the thyroid gland of unknown cause. It is often associated with other fibroproliferative disorders (e.g. mediastinal and retroperitoneal fibrosis, sclerosing cholangitis). Patients present with a rock-hard, fixed and painless goitre.
Figure 3: A patient who has Riedel's thyroiditis.
Suppurative (infectious) thyroiditis
Suppurative thyroiditis is extremely rare. Bacterial infections are the most common cause. Usually thyroid function is normal.
Immunocompromised patients and the elderly are at increased risk of developing opportunistic thyroid infections. Common symptoms of this condition are fever, dysphonia and anterior neck pain. Diagnosis is confirmed by fine-needle aspiration cytology. Appropriate parenteral antibiotics and drainage of any abscess are the appropriate treatment.
Differential diagnosis
Sudden enlargement of the thyroid gland can be due to haemorrhage. Cysts may also produce nodules on the gland. If there is enlargement of the thyroid gland the possibility of malignancy must be considered.
Brief biography or eponyms
Fritz de Quervain was a Swiss surgeon who was born in 1868 and died in 1940. De Quervain thyroiditis was first reported in 1825, but de Quervain described the pathology in 1904.
Hakaru Hashimoto was a Japanese surgeon who was born in 1881 and died 1934. His report was based on the examination of four postoperative cases that he published in 1912 when he was working in Berlin.
References
1. Shih ML, Lee JA, Hsieh CB, Yu JC et al. Thyroidectomy for Hashimoto's thyroiditis: complications and associated cancers. Thyroid 2008;18:729-34.
2. Piga M, Serra A, Boi F, Tanda ML, Martino E, Mariotti S. Amiodarone-induced thyrotoxicosis. A review. Minerva Endocrinol. 2008;33:213-28.
Author and reviewers competing interests: none.
