What is postpartum thyroiditis?

Postpartum Thyroiditis Overview

Postpartum thyroiditis is a transient autoimmune thyroid disorder occurring within the first year after delivery, characterized by sequential or isolated phases of hyperthyroidism and/or hypothyroidism, with most women returning to euthyroid status by 12 months postpartum. 1, 2, 3

Epidemiology and Pathophysiology

• The prevalence ranges from 5-9% in the general population, with a mean of 7.5% across studies 3, 4
• Women with type 1 diabetes mellitus have a three-fold increased risk 3
• This condition represents an autoimmune flare following the immune suppression of pregnancy, essentially a transient form of Hashimoto's thyroiditis 3, 5
• Up to 50% of women who are thyroid peroxidase antibody (TPO-Ab) positive in the first trimester will develop postpartum thyroiditis 4

Clinical Presentation Patterns

The classic triphasic pattern occurs in only 22% of cases 4:

• Isolated hypothyroid phase: 48% of cases 4
• Isolated thyrotoxic phase: 30% of cases 4
• Sequential hyperthyroidism followed by hypothyroidism: 22% of cases 4

Timing of Phases

• Hyperthyroid phase typically occurs around 14 weeks postpartum 6
• Hypothyroid phase typically occurs around 19 weeks postpartum 6

Symptomatology

Hyperthyroid phase symptoms:

• Lack of energy and irritability are most common 6

Hypothyroid phase symptoms (more symptomatic than hyperthyroid phase):

• Fatigue, dry skin, impaired memory, aches and pains, and cold intolerance 6, 4

Critical pitfall: Many of these symptoms overlap with normal postpartum experiences, making clinical diagnosis challenging without objective testing 2

Diagnostic Approach

Diagnosis is established by new onset of abnormal TSH level, abnormal free T4 level, or both within one year of delivery 1, 2

Who to Evaluate

• Women who develop a goiter during pregnancy or after delivery 1, 2
• Women with postpartum symptoms of hyperthyroidism or hypothyroidism (requires clinical judgment given symptom overlap with normal postpartum period) 1, 2
• Women with a history of thyroid disease 1

Confirmatory Testing

• Thyroid peroxidase antibodies (TPO-Ab) are useful for confirming the diagnosis 1, 2
• The presence of positive TPO-Ab differentiates postpartum thyroiditis from other conditions 7
• Thyroid ultrasound may show diffuse or multifocal hypoechogenicity 6

Treatment Algorithm

Hyperthyroid (Thyrotoxic) Phase

• Beta-blockers for symptomatic control when required (short course) 3, 4
• Antithyroid drugs are NOT indicated as this represents thyroid destruction, not overproduction 4
• Monitor thyroid function every 2-3 weeks to detect transition to hypothyroidism 2

Hypothyroid Phase

Treatment indications based on TSH levels:

• TSH >10 mIU/L: Levothyroxine replacement is indicated 2
• TSH 4-10 mIU/L: Consider levothyroxine if patient is symptomatic or desires fertility 2
• Adjust levothyroxine dosage to normalize TSH 2

Additional treatment considerations:

• Treatment is indicated for symptomatic relief in breastfeeding women or those attempting to conceive 4
• Objective thyroid function testing should guide treatment decisions rather than symptoms alone due to overlap with normal postpartum symptoms 2

Long-Term Prognosis and Follow-Up

Risk of Permanent Hypothyroidism

• Approximately 25-30% of women develop permanent hypothyroidism within 3 years 3, 6
• Up to 50% will be hypothyroid at 7-9 years of follow-up 6
• The risk is greatest in women with the highest TSH levels and highest antithyroid peroxidase antibody titers 1, 2
• Women who remain euthyroid postpartum despite positive TPO-Ab have only a 5% long-term risk 6

Recurrence Risk

• 70% recurrence rate in subsequent pregnancies if previous postpartum thyroiditis occurred 6
• 25% risk if the patient was euthyroid after the first pregnancy 6

Key Clinical Pitfalls

• Postpartum thyroiditis is characteristically painless, distinguishing it from subacute thyroiditis which presents with painful thyroid and pharyngeal pain 7
• Do not rely on symptoms alone for diagnosis or treatment decisions given significant overlap with normal postpartum experiences 2
• Long-term follow-up is essential as this is not a benign, self-limited condition—it carries significant risk of permanent hypothyroidism and potential cardiovascular consequences 5
• Women with preexisting Hashimoto's thyroiditis can still develop postpartum thyroiditis patterns, particularly if euthyroid in the first trimester 8