What is the diagnosis and treatment for postpartum thyroiditis in a postpartum woman?

Postpartum Thyroiditis: Diagnosis and Management

Diagnosis

Diagnose postpartum thyroiditis by detecting new onset of abnormal TSH, abnormal free T4, or both within one year of delivery, and confirm with thyroid peroxidase antibody testing. 1

Essential Diagnostic Workup

• Measure TSH and free T4 in any postpartum woman presenting with symptoms of thyroid dysfunction, depression, or who develops a goiter during pregnancy or after delivery 1
• Obtain thyroid peroxidase (anti-TPO) antibodies to confirm the autoimmune diagnosis and predict long-term risk of permanent hypothyroidism 2, 1
• If hyperthyroid, measure TSH receptor antibodies to distinguish postpartum thyroiditis from Graves' disease, particularly if ophthalmopathy is present or symptoms persist beyond the typical timeline 3
• Consider adding T3 measurement if symptoms are severe but free T4 elevation is minimal 3

Key Clinical Features

• Postpartum thyroiditis affects 5-7% of women in the first year after delivery 2
• The classic pattern is thyrotoxicosis at approximately 14 weeks postpartum followed by hypothyroidism at 19 weeks, though either phase can occur in isolation 2, 4
• Most common hyperthyroid symptoms are lack of energy and irritability 4
• Most common hypothyroid symptoms are lack of energy, aches and pains, poor memory, dry skin, and cold intolerance 4
• Screen women with postpartum depression symptoms for thyroid dysfunction, as these symptoms overlap significantly 2

Treatment Algorithm

Hyperthyroid (Thyrotoxic) Phase

Monitor thyroid function every 2-3 weeks without antithyroid drugs, as this is a destructive process, not excessive hormone production. 1, 3

• Do NOT use antithyroid drugs (methimazole or propylthiouracil) for postpartum thyroiditis—these are ineffective because the condition results from thyroid destruction, not overproduction 3
• Use beta-blockers (atenolol or propranolol) ONLY if symptomatic relief is needed 3
• Continue monitoring to catch the transition to hypothyroidism 1
• If TSH receptor antibodies are positive or ophthalmopathy is present, this indicates Graves' disease rather than postpartum thyroiditis, and thioamide therapy is then appropriate 3

Hypothyroid Phase

Initiate levothyroxine replacement for TSH >10 mIU/L; consider treatment for TSH 4-10 mIU/L if symptomatic or desiring fertility. 1

• Adjust levothyroxine dosage every four weeks until TSH returns to normal range 2, 1
• Women treated with levothyroxine can breastfeed safely 2
• Base treatment decisions on objective thyroid function testing rather than symptoms alone, as symptoms overlap with the normal postpartum period 1

Critical Long-Term Management

Women with postpartum thyroiditis face a 20-40% risk of permanent hypothyroidism within 3-10 years, with the highest risk in those with elevated TSH and anti-TPO antibodies during the acute episode. 2, 1

Follow-Up Protocol

• Reassess thyroid function at 6-12 months postpartum 2
• Women with highest TSH levels and elevated anti-TPO antibodies require longer-term periodic monitoring 1
• Recent data indicate that 50% of women who develop postpartum thyroiditis will be hypothyroid 7-9 years later 4
• The recurrence risk is 70% in subsequent pregnancies if previous postpartum thyroiditis occurred 4

Important Clinical Pitfalls

• Never use radioactive iodine (I-131) during breastfeeding; women must wait four months after treatment before resuming breastfeeding 2, 3
• Do not dismiss postpartum symptoms as "normal postpartum changes" without biochemical evaluation, especially in women with goiter or prior thyroid disease 3
• Women with preexisting euthyroid Hashimoto's thyroiditis have a 68% risk of developing postpartum thyroiditis, compared to 18% in those with hypothyroid Hashimoto's on levothyroxine 5
• First-trimester euthyroidism in women with Hashimoto's thyroiditis increases postpartum thyroiditis risk 4-fold, likely related to greater unaffected thyroid tissue available for autoimmune destruction 5