Thyroiditis

Aka: Thyroiditis, Acute Thyroiditis, Painful Thyroiditis, Painless Thyroiditis

1. Definitions
   1. Thyroiditis
      1. Thyroid Gland Inflammation with or without Thyroid dysfunction
2. Labs
   1. Precautions
      1. Serum TSH may be falsely increased or decreased by medications and non-Thyroid conditions (See Serum TSH)
      2. Fluctuating Thyroid function (initial Hyperthyroidism followed by Hypothyroidism) is typical of some Thyroiditis (see below)
   2. Initial
      1. Thyroid Stimulating Hormone (TSH)
   3. Confirmatory
      1. Free Thyroxine (Free T4)
      2. Free Triiodothyronine (Free T3)
   4. Specific tests (as indicated)
      1. Thyroid peroxidase Antibody (TPO Antibody)
         1. Increased in Hashimoto's Thyroiditis, Postpartum Thyroiditis, Silent Thyroiditis and Subacute Thyroiditis
3. Imaging
   1. Radioactive Iodine Uptake Scan (RAIU)
      1. Diffusely increased uptake in Graves Disease
      2. Decreased overall uptake in Postpartum Thyroiditis, Silent Thyroiditis or Subacute Thyroiditis
4. Causes: Most Common
   1. Hashimoto's Thyroiditis
   2. Postpartum Thyroiditis
   3. Subacute Thyroiditis
5. Causes: Painful Thyroiditis
   1. Subacute Granulomatous Thyroiditis or Giant Cell Thyroiditis (uncommon)
      1. Postviral Thyroiditis with increased Thyroid peroxidase Antibody (TPO Antibody) and low RAIU (Radioactive Iodine uptake)
      2. Resolves to euthyroid state within 85% of cases (others may continue with Hypothyroidism)
   2. Suppurative Thyroiditis or Infectious Thyroiditis (rare)
      1. Presents with Thyroid pain and tenderness, high fever, Leukocytosis and cervical adenopathy
      2. Most common infectious causes are Streptococcus Pyogenes, Streptococcus Pneumoniae and Staphylococcus aureus
   3. Radiation-Induced Thyroiditis (1% of I131 patients)
      1. Presents with transient Hyperthyroidism
   4. Traumatic Thyroiditis (rare)
      1. Self-limited Thyroiditis due to local Trauma
   5. Thyroid Hemorrhage
      1. Sudden solid Thyroid Nodule bleeding or infarction results in adjacent hemorrhagic cysts
      2. Even small hemorrhagic Thyroid cysts may cause pain, and in rare cases can cause local compression symptoms (Stridor, Dysphagia)
6. Causes: Painless Thyroiditis
   1. Hashimoto's Thyroiditis (5-10% of cases)
      1. Chronic Autoimmune Thyroiditis (or Chronic Lymphocytic Thyroiditis)
      2. Presents as Hypothyroidism (most cases) with a non-tender Goiter
      3. Thyroid peroxidase Antibody (TPO Antibody) increased
   2. Postpartum Thyroiditis (5% of cases)
      1. Hyperthyroidism or Hypothyroidism or initial Hyperthyroidism followed by Hypothyroidism
      2. Thyroid peroxidase Antibody (TPO Antibody) increased and low RAIU (Radioactive Iodine uptake)
   3. Drug-Induced Thyroiditis (10% of cases)
      1. Causes: Amiodarone, Denileukin, Interferon alfa, Interleukin-2, Kinase Inhibitors and Lithium
   4. Subacute Lymphocytic Thyroiditis or Silent Thyroiditis (uncommon)
      1. Autoimmune Thyroiditis with increased Thyroid peroxidase Antibody (TPO Antibody) and low RAIU (Radioactive Iodine uptake)
      2. Resolves to euthyroid state within 85% of cases (others may continue with Hypothyroidism) and rare recurrence
   5. Riedel's Thyroiditis or Fibrous Thyroiditis (uncommon)
      1. Firm Goiter which may be associated with local compression (Stridor, Dysphagia)
      2. Destructive Thyroiditis that may be associated with Hypocalcemia if the Parathyroid Glands are involved
7. Causes: By Thyroid function
   1. Hypothyroidism
      1. Hashimoto's Thyroiditis
      2. Riedel's Thyroiditis (euththyroid in 70% of cases)
   2. Hyperthyroidism
      1. Radiation-Induced Thyroiditis (transient)
      2. Graves Disease
   3. Hyperthyroidism followed by transient or chronic Hypothyroidism (or Hypothyroidism or Hyperthyroidism alone)
      1. Postpartum Thyroiditis
      2. Subacute Granulomatous Thyroiditis (Subacute Thyroiditis, Giant Cell Thyroiditis)
      3. Subacute Lymphocytic Thyroiditis (Silent Thyroiditis)
8. Approach: Thyroid pain
   1. Toxic appearing patient (fever, Leukocytosis, cervical adenopathy)
      1. Suppurative Thyroiditis or Infectious Thyroiditis
   2. History or local Radiation Therapy (e.g. I-131) or Trauma
      1. Radiation-Induced Thyroiditis
      2. Traumatic Thyroiditis (rare)
   3. Recent viral illness with decreased Serum TSH (and if ordered, increased Thyroglobulin)
      1. Subacute Granulomatous Thyroiditis (Subacute Thyroiditis, Giant Cell Thyroiditis)
   4. Sudden onset of Thyroid pain (with normal Thyroid Function Tests)
      1. Thyroid Hemorrhage
9. Approach: Painless Thyroiditis
   1. Taking Amiodarone, Denileukin, Interferon alfa, Interleukin-2, Kinase Inhibitors or Lithium?
      1. Drug-Induced Thyroiditis
   2. Recent pregnancy (in last year)
      1. Increased TSH
         1. Postpartum Thyroiditis (Hypothyroidism phase)
         2. Hashimoto Thyroiditis
      2. Decreased TSH with diffusely increased Radioactive Iodine Uptake Scan (RAIU)
         1. Graves Disease
      3. Decreased TSH with diffusely decreased Radioactive Iodine Uptake Scan (RAIU)
         1. Postpartum Thyroiditis (Hyperthyroidism phase)
   3. Increased TSH
      1. Hashimoto Thyroiditis
      2. Subacute Lymphocytic Thyroiditis or Silent Thyroiditis (Hypothyroidism phase)
   4. Decreased TSH with diffusely increased Radioactive Iodine Uptake Scan (RAIU)
      1. Graves Disease
   5. Decreased TSH with diffusely decreased Radioactive Iodine Uptake Scan (RAIU)
      1. Subacute Lymphocytic Thyroiditis or Silent Thyroiditis (Hyperthyroidism phase)
10. Approach: Thyroiditis with Hyperthyroidism
    1. Step 1: Based on suppressed Serum TSH
       1. Confirm Hyperthyroidism with Free T4 and Free T3
    2. Step 2: Consider recent medical history
       1. Recent illness (Euthyroid Sick Syndrome)
       2. Malnutrition or Hyponatremia risk factors
       3. Medications (e.g. Corticosteroids, Opiates, Levodopa)
    3. Step 3: Consider severity of symptoms (in confirmed Hyperthyroidism with decreased TSH and increased Free T4)
       1. Consider Beta Blockers (e.g. Propranolol) in significant Hyperthyroidism related symptoms
    4. Step 4: Distinguish Graves Disease from other Hyperthyroidism causes
       1. Obtain Radioactive Iodine Uptake Scan (RAIU)
11. Course
    1. Most Thyroiditis follows a triphasic course
       1. Hyperthyroidism phase
          1. Preformed Thyroid Hormone released from damaged Thyroid follicular cells
       2. Hypothyroidism phase
          1. Follows Thyroid Hormone store depletion
       3. Euthyroid phase
          1. Normalization of Thyroid function
12. References
    1. Bindra (2006) Am Fam Physician 73:1769-76 [PubMed]
    2. Quintero (2021) Am Fam Physician 104(6): 609-17 [PubMed]
    3. Sweeney (2014) Am Fam Physician 90(6): 389-96 [PubMed]