postpartum thyroiditis

Introduction

A variant of subacute lymphocytic thyroiditis.

Etiology

• autoimmune etiology suggested

Epidemiology

• 5-7% of normal pregnancies
• 25% of pregnant diabetics

Pathology

Morphology:

• foci of lymphocytic infiltration
• increased interstitial fibrous tissue (occasional)

Clinical manifestations

• thyroid dysfunction within the first year after delivery in a patient who had normal thyroid function before pregnancy
• 25% of affected patients present with thyrotoxicosis followed by hypothyroidism
  • the initial phase of thyrotoxicosis occurs 2-6 months postpartum, lasts 2-8 weeks, & resolves spontaneously
• 25% of patients present with isolated thyrotoxicosis
• ~50% of patients present with isolated hypothyroidism
• the hypothyroid phase occurs 3 -12 months postpartum, with permanent hypothyroidism occurring in 20%-40% of patients

Laboratory

• serum TSH is low, serum free T4 & serum T3 are elevated in thyrotoxic phase
• anti-thyroid peroxidase Ab in serum 50%
• thyroid receptor antibodies in serum are absent

Complications

• permanent hypothyroidism develops in 10-50% of affected women
  • recurrence risk is high in subsequent pregnancies.[1][4-5]

Differential diagnosis

• Graves disease:
  • thyroid receptor antibodies in serum are positive
  • other manifestations may be present
• subacute thyroiditis:
  • viral infection or postviral inflammatory process
  • pain & tenderness
  • low or undetectable anti-thyroid peroxidase Ab in serum
  • C-reactive protein in serum is generally elevated
• toxic multinodular goiter
  • more common in older patients
  • enlarged thyroid
  • autonomous thyroid hormone production from thyroid nodules

Management

• anti-microsomal Ab positive postpartum thyroiditis generally resolves in 2-4 months
• patients with postpartum thyroiditis should be monitored for development of hypothyroidism
  • antithyroid medications, such as methimazole, are not indicated because thyroid hormone synthesis is not increased
• thyroxine replacement therapy often necessary during hypothyroid phase

More general terms

• subacute lymphocytic thyroiditis
• complications of the puerperium

Additional terms

• postpartum