II. Definitions

  1. Postpartum Thyroiditis
    1. Painless Thyroiditis (with abnormal TSH) in the first 12 months following pregnancy (including Miscarriage)
    2. Does not include patients with toxic Thyroid Nodule or Grave's Disease with Thyrotropin receptor Antibody positive

III. Epidemiology

  1. Occurs in 1 to up to 10% of postpartum patients

IV. Pathophysiology

  1. Painless, autoimmune Thyroiditis
  2. Similar pathophysiology to Hashimoto's Thyroiditis
  3. Associated with HLA-DRB, HLA-DR4 and HLA-DR5
  4. Pregnancy is an Immunocompromised (or immuno-tolerant) state
  5. Postpartum Thyroiditis is concurrent with a rebound in immune function

V. Risk Factors

  1. Antithyroid Peroxidase Antibody (TPO Antibody) positive (25% risk)
    1. Associated with Thyroiditis risk, even if euthyroid
    2. Predicts recurrent Thyroiditis in future pregnancies
  2. Other autoimmune disorders (e.g. Type I Diabetes Mellitus)
  3. Postpartum Depression
  4. Family History of autoimmune Thyroiditis

VI. Types: Postpartum Thyroiditis

  1. Hypothyroidism (40%)
    1. Occurs within 12 months (typically 4-8 months) of delivery (mean: 6 months)
    2. Duration 4-6 months (although permanent Hypothyroidism occurs in 25% of women)
  2. Hyperthyroidism (30%)
    1. Occurs within 10 months (most within 6 months) of delivery (mean: 3 months)
    2. Resolves spontaneously within 2-3 months of onset
    3. Asymptomatic in one third of patients
    4. Milder than Graves Disease in those that are symptomatic
    5. Unlike Graves Disease, no Exophthalmos or Thyroid bruit and TSH Receptor Antibody negative
    6. Lower Free T3 to Free T4 ratio than with Graves Disease
  3. Triphasic: Initial Hyperthyroidism, then Hypothyroidism, then euthyroid (25% to 40%)
    1. Hyperthyroidism phase: Onset 2 to 6 months postpartum, and lasts 2 to 3 months
    2. Hypothyroidism phase: Onset 3 to 12 months postpartum

VII. Complications: Persistent Hypothyroidism (30-50%)

  1. Hypothyroidism persists or recurs within 9 years
  2. Risk factors for longterm hypothyrodism
    1. Initial Hypothyroidism at onset of thyoriditis
    2. Antithyroid Microsomal Antibody at high titer
    3. Thyroid Ultrasound with hypoechogenic pattern

VIII. Differential Diagnosis

  1. See Painless Thyroiditis
  2. Hashimoto's Thyroiditis (hypothyroid phase)
  3. Toxic Thyroid Nodule (thyrotoxic phase)
  4. Grave's Disease (thyrotoxic phase)
    1. Very important to differentiate (also presents in Postpartum Period)
    2. Thyrotropin receptor Antibody positive
      1. Contrast with TPO Antibody and Thyroglobulin Antibody present in Postpartum Thyroiditis
    3. Radioactive Iodine Uptake Scan with increased uptake

IX. Labs

X. Imaging

  1. Radioiodine Uptake (RAIU Scan)
    1. Suppressed uptake in hyperthyroid phase (Contrast with Grave's Disease in which uptake is increased)
    2. Do not perform if Breast Feeding
    3. Avoid close contact with infant following scan for period designated by imaging department
  2. Thyroid Ultrasound with doppler
    1. No increased Blood Flow (Contrast with Grave's)

XI. Management

  1. Postpartum Hyperthyroidism
    1. Beta Blockers if symptomatic (caution in Lactation)
      1. Propranolol 10-20 mg orally four times daily as needed
    2. No effect with antithyroid medications (Propylthiouracil or Methimazole)
    3. Follow TSH and T4 Free
      1. Anticipate resolution within 2-3 months
      2. May be followed by Hypothyroidism (see types above)
  2. Postpartum Hypothyroidism
    1. Levothyroxine for symptomatic Hypothyroidism, Breast Feeding or planning conception
      1. Start at 50 mcg orally daily
      2. Taper the dose after 12 months of therapy
        1. Reduce dose by 50% each cycle, followed by a recheck TSH at 4-8 weeks after each dose change
        2. Expect 75% of patients will be euthyroid off medication
    2. Follow Serum TSH
      1. Goal Serum TSH 1.0 to 2.5 mIU/L
      2. Anticipate Thyroid normalizing by 6-9 months (up to 18 months) in 80% of cases
      3. Lifelong Thyroid Replacement therapy with Levothyroxine may be required (up to 20-25% of cases)

XII. Prevention

  1. Screen pregnant women with risk factors (see above)

XIII. Prognosis

  1. Recurrence with subsequent pregnancies is common (up to 70% of cases)
  2. Risk of lifelong Hypothyroidism (15 to 50% of cases)
    1. Annual Serum TSH screening in all patients with history of Postpartum Thyroiditis

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