Thyroiditis

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)
Initial
1. Thyroid Stimulating Hormone (TSH)
Confirmatory
1. Free Thyroxine (Free T4)
2. Free Triiodothyronine (Free T3)
Specific tests (as indicated)
1. Thyroid peroxidase Antibody (TPO Antibody)
  1. Increased in Hashimoto's Thyroiditis, Postpartum Thyroiditis, Silent Thyroiditis and Subacute Thyroiditis

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)
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
Radiation-Induced Thyroiditis (1% of I131 patients)
1. Presents with transient Hyperthyroidism
Traumatic Thyroiditis (rare)
1. Self-limited Thyroiditis due to local Trauma
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)

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
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)
Drug-Induced Thyroiditis (10% of cases)
1. Causes: Amiodarone, Denileukin, Interferon alfa, Interleukin-2, Kinase Inhibitors and Lithium
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
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

Step 1: Based on suppressed Serum TSH
1. Confirm Hyperthyroidism with Free T4 and Free T3
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)
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
Step 4: Distinguish Graves Disease from other Hyperthyroidism causes
1. Obtain Radioactive Iodine Uptake Scan (RAIU)