Subacute thyroiditis
Subacute thyroiditis
Main page
1647122

Subacute thyroiditis

logo
Community Hub0 subscribers
Read side by side
Subacute thyroiditis
View on Wikipedia
from Wikipedia
Subacute thyroiditis
Micrograph showing a granuloma in subacute granulomatous thyroiditis. H&E stain.
SpecialtyEndocrinology Edit this on Wikidata

Subacute thyroiditis refers to a temporal classification of the different forms of thyroiditis based on onset of symptoms.[1][2][3][4][5][6][7] The temporal classification of thyroiditis includes presentation of symptoms in an acute, subacute, or chronic manner.[1][2][3][4][5] There are also other classification systems for thyroiditis based on factors such as clinical symptoms and underlying etiology.[2][4]

Broadly, there are three categories of thyroiditis that can present in a subacute fashion, including subacute granulomatous thyroiditis, subacute lymphocytic thyroiditis, and drug-induced thyroiditis.[3][4] In all three categories, there is inflammation of the thyroid gland causing damage to the thyroid follicular cells which produce and secrete thyroid hormone. This often results in three phases of thyroid dysfunction beginning with initial thyrotoxicosis followed by hypothyroidism before resolution back to normal thyroid function.[1][2][3][4][5] In the thyrotoxic stage, individuals usually complain of fever, myalgia, and may have associated anterior neck pain among other symptoms.[1][2][3][4] In the hypothyroid stage, they may be asymptomatic or experience mild symptoms.[2] In most cases, the thyroid dysfunction is transient and people recover with symptomatic treatment.[1][2][3][4]

Etiology

[edit]

Among the different classification systems for thyroiditis, the onset of symptoms can be used to classify thyroiditis as acute, subacute, or chronic.[1][2][3][4][5] The three types of thyroiditis that can occur in a subacute manner include subacute granulomatous thyroiditis, subacute lymphocytic thyroiditis, and drug-induced thyroiditis.[3][4]

Subacute granulomatous thyroiditis affects more women than men and often follows a viral upper respiratory tract infection with many implicated viruses including Coxsackievirus, Epstein-Barr virus, and recently SARS-CoV-2 among others.[2][3][8]

Subacute lymphocytic thyroiditis, also called painless or silent thyroiditis, occurs in individuals with underlying autoimmune disease or after pregnancy.[2][4][5] It is considered to be a variant of Hashimoto's thyroiditis. When subacute lymphocytic thyroiditis occurs up to 12 months postpartum, it is called postpartum thyroiditis. It has an increased incidence in women with presence of thyroid peroxidase (TPO) antibodies prior to pregnancy and in women with preexisting Type 1 diabetes. Postpartum thyroiditis can recur in subsequent pregnancies.[2][4][5]

Drug-induced thyroiditis can occur in individuals receiving certain therapies such as amiodarone, interferon-alpha, lithium, tyrosine-kinase inhibitors, and immunotherapies among other drugs. These individuals may develop subacute lymphocytic thyroiditis.[2][3][4][5]

Pathophysiology

[edit]

In all three types of thyroiditis, there is inflammation of the thyroid gland which leads to clinical symptoms in three phases. The initial thyrotoxic phase is followed by hypothyroid phase before reaching a euthyroid phase where normal thyroid function in restored.[1][2][3][4][5][7] The timing of each phase varies and not every person experiences all three phases.[1][3][4][5] In the thyrotoxic phase, the follicular cells of the thyroid gland are damaged leading to release of pre-formed thyroid hormone and symptoms of thyrotoxicosis. The damage to the follicles impairs ability to produce and secrete thyroid hormones which then leads to a hypothyroid phase.[1][3][4][5][7] As inflammation resolves, the thyroid follicles regenerate and begin to produce thyroid hormones once again.[3]

In subacute granulomatous thyroiditis, there is infiltration of neutrophils and other immune cells which cause damage to the thyroid follicular cells. The damage leads to formation of granulomas with multi-nucleated giant cells and associated fibrosis.[3][4][5][8] In contrast, subacute lymphocytic thyroiditis is characterized by an infiltration of lymphocytes causing damage to the thyroid gland, similar to Hashimoto's thyroiditis.[8]

Signs and symptoms

[edit]

The symptoms of subacute thyroiditis depend on the etiology. In subacute granulomatous thyroiditis, there may be a history of a viral infection preceding onset of symptoms.[1][2][3][4][5][6][8] The presenting symptom is usually anterior neck pain that may be unilateral or bilateral with radiation to jaw or ears. Individuals can also experience dysphagia due to diffusely enlarged thyroid gland.[2][3][4][5][8] There are often associated systemic symptoms of fever, malaise, and arthralgia. The thyrotoxic phase can last for 3–6 weeks during which some may experience mild symptoms associated with elevated thyroid hormones as they leaks out of the damaged thyroid gland. During this phase, one can experience diaphoresis, tremors, heat intolerance, or weight loss.[2][3][4][5][7][8] Upon examination, the thyroid gland is often firm, diffusely enlarged, and tender to palpation. The thyroid may be smooth or nodular.[1][2][3][4][5] As the thyroid hormone stores are depleted, about a third of the individuals will enter a hypothyroid phase which may last up to six months. There is no neck pain in the hypothyroid phase and little to no other symptoms.[2] Most people return to normal thyroid function within one year of symptom onset; however, between 5-15% of individuals develop permanent hypothyroidism.[2][3][4][5] Some individuals may also have relapse of symptoms.[4]

In those with subacute lymphocytic thyroiditis, the thyroid gland is not tender to palpation (hence the name of painless or silent thyroiditis).[1][4][5] The thyroid gland may be firm, finely nodular, and may or may not be diffusely enlarged.[4][5] Similar to subacute granulomatous thyroiditis, there is an initial transient thyrotoxic phase that can last 2–5 months followed by a hypothyroid phase. Thyrotoxic symptoms are usually mild and in some individuals, the hypothyroid phase is the only symptomatic phase.[4][5][7] In the hypothyroid phase, patient may experience cold intolerance, fatigue, weight gain, or depression. The hypothyroidism may or may not resolve spontaneously.[5]

Those who develop drug-induced thyroiditis may have clinical course similar to subacute lymphocytic thyroiditis or other forms of thyroiditis.[5]

Diagnosis

[edit]

The diagnosis of subacute thyroiditis can be made clinically by eliciting risk factors, associated symptoms, and physical examination.[1][2][3] Further work-up to differentiate between the etiologies of subacute thyroiditis can include: thyroid function tests (TFTs), inflammatory markers, complete blood count (CBC), and thyroid antibodies.[1][2][3] Additionally, radioactive iodine uptake (RAIU) and scan can be performed in the thyrotoxic stage to help differentiate between other causes of thyrotoxicosis.[1][2][3][4][5]

In subacute granulomatous thyroiditis, a prodrome of a viral illness, painful thyroid, and symptoms of thyrotoxicosis may be present.[1][2][3] Thyroid function test will evolve through the three phases of thyrotoxicosis, hypothyroidism, and euthyroid state. In the thyrotoxic phase, thyroid stimulating hormone (TSH) will be low with high or normal levels of thyroid hormones. Inflammatory markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are elevated.[1][2][3][4][5] RAIU will be low in the thyrotoxic phase which helps to distinguish subacute granulomatous thyroiditis from other cause of thyrotoxicosis such as Graves' disease.[1][2][3][4][5][7] White blood count is usually normal or mildly elevated and there are no thyroid antibodies present.[3][4][5] Thyroid imaging and fine needle aspiration (FNA) are usually not needed for diagnosis.[3][4]

In subacute lymphocytic thyroiditis, thyroid function tests will also evolve through the phases and RAIU will be low in the thyrotoxic phase.[4][5] It can be distinguished from subacute granulomatous thyroiditis by lack of pain, presence of TPO or thyroglobulin (Tg) antibodies, and normal inflammatory markers.[4][5] Fine needle aspiration (FNA) should be performed in patients who also have a thyroid nodule to rule out thyroid cancer.[5]

Treatment

[edit]

The goal of treatment of subacute thyroiditis is to help reduce pain and symptoms of thyrotoxicosis.[1][2][3][4][5] In drug-induced thyroiditis, management begins with discontinuation of the offending drug followed by symptomatic treatment.[2] First line treatment for pain is high doses of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen. Acetylsalicylic acid such as aspirin may also be used in high doses. If symptoms are severe and there is no relief with NSAIDs or acetylsalicylic acid, corticosteroids such as prednisone can be used.[2][3][4][5] Beta blockers such as propranolol can be used for severe symptoms related to elevated thyroid hormone in all three categories of subacute thyroiditis.[1][4] There is no role for antithyroid drugs since the thyrotoxic phase is due to a transient process.[1][2][3][4][5] Replacement of thyroid hormone with levothyroxine may be needed in patients who develop a hypothyroid phase.[2][3][4][5] Annual followup is recommended for these individuals due to risk of recurrence and development of permanent hypothyroidism.[5]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Subacute thyroiditis

View on Grokipedia
from Grokipedia
Subacute thyroiditis, also known as de Quervain's thyroiditis or granulomatous thyroiditis, is a self-limited inflammatory disorder of the thyroid gland that typically follows a viral upper respiratory infection, including recent associations with SARS-CoV-2, and is characterized by painful thyroid enlargement, fever, and transient phases of thyrotoxicosis followed by hypothyroidism.[1][2] The condition involves granulomatous inflammation with giant cell infiltration and disruption of thyroid follicles, leading to the release of preformed thyroid hormones into the bloodstream.[3] It most commonly affects women aged 30 to 50 years, with an incidence of approximately 4.9 cases per 100,000 people annually, and is more prevalent in regions with higher viral infection rates during certain seasons.[1][3][4] Clinically, subacute thyroiditis presents with acute anterior neck pain that may radiate to the jaw or ears, accompanied by systemic symptoms such as fatigue, malaise, low-grade fever (up to 104°F or 40°C), and myalgias.[1][2] Early in the course, patients often experience symptoms of thyrotoxicosis, including palpitations, heat intolerance, weight loss, and tachycardia, due to the leakage of thyroid hormones; this is followed by a hypothyroid phase with fatigue, weight gain, and cold intolerance as the inflamed gland temporarily underproduces hormones.[3][1] Physical examination reveals a tender, firm, and asymmetrically enlarged thyroid gland.[2] The disease duration typically spans 1 to 3 months for the hyperthyroid phase and up to 6 months overall, with recurrences in approximately 20% of cases.[3] Diagnosis is primarily clinical, based on history and presentation, and confirmed by laboratory findings including suppressed thyroid-stimulating hormone (TSH), elevated free thyroxine (T4) and triiodothyronine (T3) in the initial phase, markedly elevated erythrocyte sedimentation rate (ESR, often >50 mm/h), and low radioactive iodine uptake (RAIU, <5% at 24 hours).[1][3] Thyroid ultrasound may show heterogeneous hypoechoic areas, and fine-needle aspiration, if performed, reveals multinucleated giant cells, though it is not routinely needed.[2] Differential diagnosis includes acute suppurative thyroiditis, which has higher fever and leukocytosis, and silent thyroiditis, which lacks pain.[3] Treatment focuses on symptom relief, as the condition is self-resolving in over 90% of cases.[1] Nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, are first-line for mild pain and inflammation, while corticosteroids like prednisone (initial dose 40 mg/day, tapered over 4-6 weeks) are used for severe symptoms or when NSAIDs fail.[2][3] Beta-blockers (e.g., propranolol) manage thyrotoxic symptoms, and levothyroxine replacement is provided if hypothyroidism persists beyond 3 months.[1] Antithyroid drugs are ineffective and not recommended, as hyperthyroidism results from hormone release rather than overproduction.[3] The prognosis is excellent, with full recovery of thyroid function in most patients within 12 months, though 5-15% may develop permanent hypothyroidism requiring lifelong therapy.[2][1][5] Complications are rare but can include chronic hypothyroidism or, infrequently, atrial fibrillation during the thyrotoxic phase.[3] Early recognition and supportive care are key to alleviating discomfort and preventing unnecessary interventions.[2]

Background

Definition and synonyms

Subacute thyroiditis is a self-limited inflammatory disorder of the thyroid gland characterized by granulomatous inflammation, typically presenting with painful thyroid enlargement and systemic symptoms, and following a triphasic course of transient hyperthyroidism, hypothyroidism, and eventual recovery to euthyroidism.[6] This condition is classified as a form of painful thyroiditis, distinguishing it from other types through its granulomatous histology and self-resolving nature.[7] Common synonyms for subacute thyroiditis include de Quervain's thyroiditis, subacute granulomatous thyroiditis, giant cell thyroiditis, and subacute nonsuppurative thyroiditis.[6] It is differentiated from acute suppurative thyroiditis, which involves bacterial infection and pus formation leading to abscesses, and from chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), an autoimmune condition characterized by lymphocytic infiltration without granulomas or significant pain.[8] The eponym "de Quervain's thyroiditis" derives from the 1904 description by Swiss surgeon Fritz de Quervain, who first characterized the disorder as a subacute nonsuppurative thyroiditis based on its distinctive pathological features.[9]

Epidemiology

Subacute thyroiditis has an estimated incidence of 4.9 to 12.1 cases per 100,000 person-years, based on long-term cohort data from iodine-sufficient regions such as the United States.[8] In more recent assessments from the same cohort (1970-1997), the age- and sex-adjusted incidence rose to 12.1 cases per 100,000 person-years, with rates notably higher among women at 19.1 per 100,000 compared to 4.1 per 100,000 in men.[8] These figures underscore the condition's relative rarity compared to other thyroid disorders, accounting for approximately 5% of thyroid-related presentations in clinical settings.[10] The disease predominantly affects individuals aged 25 to 50 years, with a peak incidence in the fourth and fifth decades of life.[11] It is rare in children and the elderly, with cases under 20 years or over 70 years comprising less than 5% of reported instances.[8] A marked female predominance is observed, with a female-to-male ratio ranging from 3:1 to 5:1 across multiple studies, reflecting potential hormonal or immune-related influences on susceptibility.[11][12] Epidemiological data are primarily reported from iodine-sufficient regions such as North America and Europe.[8] Seasonal patterns reveal peaks in summer and early autumn, coinciding with increased enteroviral activity, as evidenced by Italian data indicating 66% of cases from June to September.[13][14] During the COVID-19 pandemic from 2020 to 2022, reports of subacute thyroiditis surged, with incidence rates among COVID-19 survivors reaching 17.28 per 100,000—nearly double that of non-infected controls—and elevated proportions in thyroid clinics (up to 3% in 2020 versus 1.7-1.9% pre-pandemic).[15][16] This trend included numerous post-vaccination cases, predominantly following mRNA vaccines, comprising over 60% of vaccine-associated thyroid disorders in systematic reviews of more than 50 reported instances.[17][18]

Causes and mechanisms

Etiology

Subacute thyroiditis is primarily triggered by a post-viral inflammatory process, with many patients reporting a preceding upper respiratory tract infection 2 to 8 weeks earlier.[19] Stress does not directly cause thyroid swelling but can act as a trigger or exacerbating factor for autoimmune thyroid conditions such as Graves' disease, which often leads to thyroid enlargement (goiter) or swelling. Subacute thyroiditis may also be influenced by stress in some cases. A sensation of thyroid swelling under stress could stem from these disorders or related muscle tension, but it requires medical evaluation to identify the underlying cause, as it may indicate inflammation or other issues.[20][21] This condition has been associated with various viral pathogens, including coxsackievirus, mumps, measles, adenovirus, and influenza.[3] Subacute thyroiditis has been reported following COVID-19 infection and, in multiple case reports, after COVID-19 vaccination (particularly mRNA types like Pfizer-BioNTech). Symptom onset ranges from days to several weeks post-vaccination (e.g., 2-39 days in some series), with features including neck pain, thyrotoxicosis (palpitations, anxiety, fatigue, weight loss), and potential progression to hypothyroidism. While large population studies as of 2024-2025 have not demonstrated an overall increased incidence or recurrence risk attributable to vaccination, these temporal associations suggest possible immune-mediated triggers in susceptible individuals, akin to post-viral etiology. Diagnosis and management remain similar to classic cases, with most resolving spontaneously or with supportive care.[22][23] Genetic factors contribute significantly to susceptibility, with the HLA-B35 allele identified in approximately 70% of affected individuals across various populations.[24] Additional genetic links include the HLA-B18:01 allele and the HLA-DRB101 haplotype, which may influence disease recurrence or severity in predisposed groups.[25] Rare cases of subacute thyroiditis have been linked to drug exposure, particularly interferon-alpha used in treatments for hepatitis C or malignancies.[26] Direct viral invasion of thyroid tissue has not been demonstrated; rather, the etiology involves an immune-mediated response triggered by the infection.[27]

Pathophysiology

Subacute thyroiditis, also known as subacute granulomatous thyroiditis or de Quervain's thyroiditis, involves an immune-mediated inflammatory process that disrupts thyroid follicular architecture. Although often preceded by viral triggers such as upper respiratory infections, the condition is characterized by a granulomatous response without direct evidence of viral replication within thyroid tissue, as no viral particles or inclusion bodies have been identified in affected glands.[3][11] This inflammation is driven by cytotoxic T lymphocytes and other immune cells targeting follicular cells, leading to epithelial disruption and release of stored thyroid hormones.[11] The process is associated with genetic factors, including the HLA-B35 allele, which predisposes individuals to this immune dysregulation.[24] Histologically, the thyroid exhibits granulomatous inflammation featuring multinucleated giant cells, epithelioid histiocytes, lymphocytes, and plasma cells surrounding disrupted follicles.[3] These granulomas form as a response to follicular damage, with early stages showing extensive infiltration and colloid depletion, while later phases involve progressive fibrosis and partial glandular regeneration.[11] Fine-needle aspiration typically reveals these characteristic giant cells and mixed inflammatory infiltrates, confirming the granulomatous nature without neoplastic changes.[24] The hormonal perturbations arise from the destructive inflammation, resulting in a classic triphasic progression. Initially, the thyrotoxic phase occurs due to leakage of preformed thyroxine (T4) and triiodothyronine (T3) from damaged follicles, typically lasting 4-10 weeks and accompanied by suppressed thyroid-stimulating hormone (TSH) levels.[3] This is followed by a hypothyroid phase, stemming from depletion of stored hormones and temporary inhibition of new synthesis amid ongoing inflammation, which may persist for 2-6 months and is often subclinical.[11] Recovery ensues through follicular regeneration and resolution of inflammation, with 85-95% of patients achieving euthyroidism within 12 months, though a minority develop permanent hypothyroidism due to extensive fibrosis.[24]

Clinical features

Signs and symptoms

Subacute thyroiditis typically presents with acute onset of anterior neck pain, which is the hallmark symptom and occurs in approximately 96% of cases. This pain is often severe and may radiate to the jaw, ears, or upper chest, exacerbated by swallowing, coughing, or head movement, and can migrate from one thyroid lobe to the other in a pattern known as "creeping thyroiditis." The thyroid gland is usually enlarged, forming a diffuse goiter that is tender and firm on palpation, though specific prevalence rates for goiter vary across studies but are commonly reported in the majority of patients.[6][3] Systemic symptoms frequently accompany the local pain, including low-grade fever in about 54% of patients, malaise, fatigue, myalgias, and arthralgias, which contribute to a flu-like illness. These features often precede or coincide with the neck discomfort and can be prominent enough to mimic an infectious process.[3][8] In the initial phase, approximately 47% of patients exhibit symptoms of transient thyrotoxicosis, such as palpitations, tachycardia, heat intolerance, tremor, anxiety, and weight loss, due to the release of stored thyroid hormones. These hypermetabolic signs typically last 2 to 8 weeks before potentially evolving into a hypothyroid phase.[3][6]

Disease phases

Subacute thyroiditis typically progresses through three distinct phases, characterized by evolving thyroid hormone levels and associated symptoms. The initial thyrotoxic phase arises from the release of preformed thyroid hormones due to follicular damage and generally lasts 4 to 8 weeks. During this period, patients may experience hyperthyroid symptoms such as tachycardia, heat intolerance, nervousness, and weight loss, with exaggerated manifestations like atrial fibrillation occurring more frequently in older individuals. This phase resolves spontaneously as hormone stores deplete, without requiring intervention beyond symptom management.[11] The hypothyroid phase follows in approximately 20% to 50% of cases, typically emerging after the thyrotoxic stage and persisting for 2 to 6 months. Symptoms during this time include fatigue, cold intolerance, constipation, dry skin, lethargy, and depression, reflecting depleted thyroid hormone reserves. This phase is often mild and self-limited, though it can cause significant discomfort if prolonged.[28][11] Most patients enter a recovery phase thereafter, with euthyroid function returning in 85% to 95% of cases by 6 to 12 months from onset. Full restoration of normal thyroid hormone production occurs as inflamed tissue heals and follicles regenerate, though irregular scarring may occasionally impair function. Permanent hypothyroidism develops in only 5% to 10% of individuals, usually due to extensive follicular destruction.[3][29][28] The overall risk of recurrence is low, affecting about 4% of patients, but it is substantially higher among those carrying the HLA-B35 allele, with up to a sixfold increased likelihood.[11][28]

Diagnosis

Laboratory evaluation

Laboratory evaluation of subacute thyroiditis primarily involves assessing thyroid function, inflammatory markers, and autoantibodies to support diagnosis and distinguish it from other forms of thyroiditis. Thyroid function tests reveal a characteristic triphasic pattern that aligns with the disease phases, beginning with a thyrotoxic stage followed by hypothyroidism and eventual recovery.[1][30] In the initial thyrotoxic phase, thyroid-stimulating hormone (TSH) levels are suppressed, often below 0.05 μIU/mL, while free thyroxine (T4) and triiodothyronine (T3) are elevated, reflecting release of preformed hormones from damaged follicles.[30] As the condition progresses to the hypothyroid phase, TSH rises significantly, and free T4 levels fall below normal, sometimes accompanied by low T3.[1] Over time, typically within months, thyroid function normalizes in most patients, with serial testing every 2-4 weeks recommended to monitor this evolution.[1] The total T3:T4 ratio is often less than 20 during this phase, aiding differentiation from Graves disease.[30] Inflammatory markers are markedly elevated, providing key evidence of the granulomatous inflammation. Erythrocyte sedimentation rate (ESR) exceeds 50 mm/h in approximately 90% of cases and frequently surpasses 100 mm/h, serving as a hallmark finding that helps distinguish subacute thyroiditis from painless or postpartum variants where ESR is normal.[30] C-reactive protein (CRP) levels are also raised during the acute phase, correlating with disease activity and often paralleling ESR trends.[31] These elevations typically resolve with clinical improvement.[30] Autoantibody testing is essential to rule out autoimmune thyroid diseases. Antithyroperoxidase (anti-TPO) and antithyroglobulin (anti-Tg) antibodies are usually absent or present at low titers, with transient positivity in approximately 15% for anti-TPO and 40-60% for anti-Tg during the early phase; such findings do not indicate underlying autoimmune thyroiditis.[30][32] Additional laboratory findings may include mild anemia and leukocytosis, reflecting the systemic inflammatory response, though these are nonspecific and occur in a subset of patients.[11] Thyroglobulin levels are elevated in over 90% of cases during the early and active phases due to follicular disruption but tend to normalize in the recovery phase.[33]

Imaging and biopsy

Ultrasound is a primary non-invasive imaging modality for evaluating subacute thyroiditis, revealing characteristic hypoechoic and heterogeneous areas within the thyroid gland, often with ill-defined margins and a lack of discrete nodular shape.[34] These findings reflect the inflammatory involvement, and color Doppler ultrasound typically demonstrates reduced vascularity or avascularity in the affected regions during the acute phase, distinguishing it from hypervascular conditions like Graves' disease.[35] Ultrasound is also useful for identifying rare complications such as nodules or abscess formation, though these are uncommon in subacute thyroiditis.[36] Nuclear scintigraphy, particularly with technetium-99m pertechnetate or iodine-123, plays a key role in confirming the functional impact of subacute thyroiditis by showing low radioactive iodine uptake (RAIU), typically less than 5-10% at 24 hours during the thyrotoxic phase.[30] This reduced uptake results from inhibited thyroid hormone synthesis due to follicular cell damage and release of preformed hormone stores, as detailed in the pathophysiology section.[37] Scintigraphic images often display patchy or globally decreased tracer uptake in the thyroid, aiding differentiation from other causes of thyrotoxicosis with normal or high RAIU.[38] Fine-needle aspiration (FNA) biopsy is not routinely required for diagnosing subacute thyroiditis but is indicated when malignancy is suspected, such as in cases of a persistent solitary nodule or atypical presentation.[30] Cytological examination of FNA samples typically reveals multinucleated giant cells, epithelioid histiocytes, and a mixed inflammatory infiltrate including lymphocytes and plasma cells, with fragmented colloid material in the background.[39] These features, particularly the presence of giant cells in nearly all cases, support the granulomatous inflammatory nature of the condition and help rule out neoplastic processes.[40] Computed tomography (CT) or magnetic resonance imaging (MRI) is uncommonly employed in subacute thyroiditis, reserved for assessing potential extrathyroidal extension or complications in severe cases, though such extension is rare due to the self-limited inflammatory process.[41] On CT, the thyroid may appear enlarged with heterogeneous attenuation, while MRI can highlight edematous changes as areas of high signal intensity on T2-weighted images, aiding in exclusion of alternative pathologies like abscess or tumor invasion.[30] Recent advances as of 2025 include proposed diagnostic criteria requiring two major features (e.g., elevated ESR or CRP; ultrasound hypoechoic areas with reduced vascularity) plus at least one supporting finding (e.g., low RAIU, typical FNA); emerging tools such as contrast-enhanced ultrasound for differentiating from malignancy and biomarkers like hepcidin (AUC 0.735 for diagnosis) are being investigated.[42]

Management and outcomes

Treatment approaches

Treatment of subacute thyroiditis is primarily symptomatic and supportive, focusing on alleviating pain, inflammation, and thyroid hormone-related symptoms while avoiding therapies that target hormone synthesis, as the condition involves hormone release rather than overproduction.[26] The approach is tailored to the disease phase, with most cases resolving spontaneously within 3-6 months.[6] For pain and inflammation management, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen at 400-800 mg every 8 hours are recommended as first-line therapy for mild to moderate symptoms.[6] In severe or refractory cases, corticosteroids like prednisone at 40 mg daily are used, followed by a taper of 5-10 mg weekly over 4-6 weeks to minimize recurrence risk during withdrawal.[6][3] During the hyperthyroid phase, beta-blockers such as propranolol at 10-40 mg every 6-8 hours are employed to control symptoms like tachycardia and tremors, titrated to effect.[26] Antithyroid drugs are not indicated, as there is no excess thyroid hormone synthesis.[26] In the hypothyroid phase, levothyroxine supplementation at 50-100 mcg daily is provided if patients are symptomatic or have TSH levels above 10 mIU/L, with discontinuation attempted after 1-2 months upon recovery of thyroid function.[6][26] Adjunctive measures include analgesics for additional pain relief and rest to support recovery.[6] Surgery is rarely required, occurring in less than 1% of cases, typically for complications such as abscess formation or unremitting pain unresponsive to medical therapy.[3]

Prognosis and complications

Subacute thyroiditis is generally a self-limited condition, with full recovery of thyroid function occurring in 85-95% of cases.[43][26] The median duration of the disease is 4-6 months, encompassing the thyrotoxic, hypothyroid, and recovery phases, after which most patients return to euthyroidism.[3][29] Complications are uncommon but can include transient atrial fibrillation during the thyrotoxic phase, affecting approximately 5% of patients due to the associated hyperthyroxinemia.[11] Permanent hypothyroidism develops in 5-10% of cases, typically resulting from extensive follicular destruction, and may require lifelong levothyroxine replacement.[26][44] Rare complications include thyroid fibrosis in severe or recurrent cases, which can impair gland function, and coexistence of papillary thyroid carcinoma, reported in up to 4.4% of patients in some biopsied cohorts, though the association is likely coincidental and remains under investigation.[45][46][11] Recurrence occurs in 1-4% of patients overall, though rates may reach up to 20% in certain populations, and is strongly associated with the HLA-B35 allele, particularly when co-occurring with HLA-B*18:01.[47][48] Case reports have described subacute thyroiditis following COVID-19 infection or vaccination, potentially due to immune dysregulation, but large population studies as of 2024 have not found an increased incidence or recurrence risk.[49][50][51] Monitoring involves follow-up thyroid function tests every 4-6 weeks until normalization to detect persistent hypothyroidism or recurrence early.[14] Treatment with corticosteroids can reduce the duration of symptoms, though it does not alter the overall prognosis in most cases.[26]

References

  1. Subacute Thyroiditis - Endocrine and Metabolic Disorders
  2. Subacute thyroiditis: MedlinePlus Medical Encyclopedia
  3. Subacute Thyroiditis - Endotext - NCBI Bookshelf - NIH
  4. https://academic.oup.com/jcem/article/88/5/2100/2845301
  5. https://emedicine.medscape.com/article/125648-clinical
  6. De Quervain Thyroiditis - StatPearls - NCBI Bookshelf - NIH
  7. Subacute thyroiditis - Pathology Outlines
  8. Acute and Subacute, and Riedel's Thyroiditis - Endotext - NCBI - NIH
  9. Subacute Granulomatous Thyroiditis: de Quervain's Diseases
  10. Emerging trends and hot spots in subacute thyroiditis research from ...
  11. Subacute Thyroiditis: Practice Essentials, Pathophysiology, Etiology
  12. Impact of the COVID-19 pandemic on the incidence, seasonal ...
  13. High prevalence of subacute thyroiditis during summer season in Italy
  14. Subacute thyroiditis - Symptoms, Causes, Images, and ... - Epocrates
  15. Investigating the Incidence of Subacute Thyroiditis in Long COVID ...
  16. Incidence of Subacute Thyroiditis During the COVID-19 Pandemic in ...
  17. Subacute thyroiditis after COVID-19 vaccination: A systematic review ...
  18. Thyroid dysfunction following vaccination with COVID-19 ... - PMC
  19. Subacute thyroiditis - UpToDate
  20. What is the impact of stress on the onset and anti-thyroid drug therapy in patients with graves' disease: a systematic review and meta-analysis
  21. Stress triggers the onset and the recurrences of hyperthyroidism in patients with Graves' disease
  22. https://pmc.ncbi.nlm.nih.gov/articles/PMC8686178/
  23. https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2025.1699210/full
  24. The Old and the New in Subacute Thyroiditis: An Integrative Review
  25. A Novel Finding of an HLA Allele's and a Haplotype's Relationship ...
  26. Thyroiditis: Evaluation and Treatment - AAFP
  27. Subacute Thyroiditis—Is it Really Linked to Viral Infection?
  28. Subacute thyroiditis - Symptoms, diagnosis and treatment
  29. Thyroiditis: Types, Causes, Symptoms, Diagnosis & Treatment
  30. Subacute Thyroiditis Workup - Medscape Reference
  31. Thyroiditis: An Integrated Approach | AAFP
  32. https://pmc.ncbi.nlm.nih.gov/articles/PMC6873036/
  33. Serum Thyroglobulin Levels in the Diagnosis and Follow-up of ...
  34. Ultrasonographic Characteristics of Subacute Granulomatous ... - NIH
  35. Sonographic Pattern of Subacute Thyroiditis Is HLA-Dependent
  36. Painful Subacute Thyroiditis is Commonly Misdiagnosed as ...
  37. Thyroid Uptake and Scan - StatPearls - NCBI Bookshelf - NIH
  38. Nodular Goiter, Hypothyroidism, and Subacute Thyroiditis
  39. Fine-Needle Aspiration of De Quervain's Thyroiditis (Subacute ... - NIH
  40. Fine Needle Aspiration Cytology of Subacute Granulomatous ...
  41. CT and MR Imaging Findings Associated with Subacute Thyroiditis
  42. Advances in Subacute Thyroiditis: Pathogenesis, Diagnosis, and ...
  43. Subacute Thyroiditis: Clinical Presentation and Long Term Outcome
  44. Clinical Aspects in Subacute Thyroiditis: A Real-Life Study on 226 ...
  45. New aspects in the pathogenesis and management of subacute ...
  46. Prevalence of papillary thyroid cancer in subacute ... - PubMed
  47. Incidence of subacute thyroiditis recurrences after a prolonged latency
  48. The Risk of Recurrence of Subacute Thyroiditis Is HLA-Dependent
  49. Subacute Thyroiditis after COVID-19: A Literature Review - PMC
  50. Subacute thyroiditis following COVID-19: A systematic review
  51. https://pubmed.ncbi.nlm.nih.gov/38729568/
User Avatar
No comments yet.