Postpartum Thyroiditis

Background

• Postpartum thyroiditis is an inflammatory autoimmune disorder causing thyroid dysfunction (excluding Graves disease) in the first postpartum year in women who were typically euthyroid before pregnancy.
• Clinical presentation of postpartum thyroiditis can vary. The classic (biphasic) clinical course is characterized by transient thyrotoxicosis, followed by transient hypothyroidism, and then a return to euthyroidism by the end of the first postpartum year. Women with postpartum thyroiditis may also present with isolated thyrotoxicosis or isolated hypothyroidism before typically reverting to euthyroidism.
• Most women are reported to spontaneously recover from postpartum thyroiditis. However, 2%-21% of women with postpartum thyroiditis are reported to have permanent hypothyroidism 12 months after delivery, with rates of permanent hypothyroidism as high as 54% in women living in an area of mild iodine deficiency.

Evaluation

• If postpartum thyroiditis is suspected, perform blood testing.
  • Measure thyroid-stimulating hormone (TSH) and free thyroxine to assess thyroid function.
  • If TSH is low, measure total tri-iodothyronine (if total tri-iodothyronine assay is not available, measure free tri-iodothyronine).
  • Assess for thyroid peroxidase antibodies.
• In women who develop thyrotoxicosis after delivery, test to distinguish postpartum thyroiditis from postpartum Graves disease (Strong recommendation).
  • Measure TSH receptor antibodies (TRAb) (Strong recommendation).
  • If needed:
    • Assess thyroidal blood flow on ultrasound (Strong recommendation).
    • Determine radioactive iodine uptake (Strong recommendation).

Management

• During the thyrotoxic phase of postpartum thyroiditis:
  • Treat patients with symptomatic thyrotoxicosis with beta-blockers safe for lactating women (propranolol or metoprolol) at the lowest dose possible (typical treatment duration is a few weeks) (Strong recommendation).
  • Antithyroid medications are not recommended for the treatment of the thyrotoxic phase of postpartum thyroiditis (Strong recommendation).
• Following the thyrotoxic phase, screen for the hypothyroid phase by measuring TSH every 4-8 weeks or if new symptoms develop (Strong recommendation).
• During the hypothyroid phase of postpartum thyroiditis:
  • Levothyroxine is suggested for (Weak recommendation):
    • women with symptomatic hypothyroidism due to postpartum thyroiditis
    • women with hypothyroidism who are attempting pregnancy or are breastfeeding
    • asymptomatic women with TSH persisting above reference range at 4-8 weeks of follow-up
  • Consider discontinuing levothyroxine therapy after 12 months, but avoid tapering off in women who are attempting pregnancy or are already pregnant (Weak recommendation).
  • If treatment not started, consider rechecking TSH every 4-8 weeks until thyroid function normalizes (Weak recommendation).
• In women with a history of postpartum thyroiditis, test TSH annually for permanent hypothyroidism (Strong recommendation).