In a postpartum woman within the first year after delivery with suppressed thyroid‑stimulating hormone (TSH), markedly elevated free triiodothyronine (free T3) and normal free thyroxine (free T4), what is the recommended management?

Postpartum Hyperthyroidism with High FT3, Normal FT4, and Low TSH: Management

Immediate Diagnostic Confirmation

This biochemical pattern in the postpartum period most likely represents postpartum thyroiditis in its hyperthyroid (thyrotoxic) phase, which requires observation and symptomatic management only—not antithyroid drugs. 1

The key diagnostic steps are:

• Measure TSH receptor antibodies (TRAb) and thyroid peroxidase antibodies (anti-TPO) to distinguish postpartum thyroiditis from Graves' disease, as this fundamentally changes management 1
• Obtain radioactive iodine uptake (RAIU) if available and not breastfeeding, as postpartum thyroiditis shows low uptake while Graves' disease shows elevated uptake 1
• Check for ophthalmopathy (proptosis, lid lag, periorbital edema), which is diagnostic of Graves' disease and warrants immediate endocrine referral 1

Management Based on Etiology

If Postpartum Thyroiditis (Most Likely)

Antithyroid drugs are NOT indicated for postpartum thyroiditis because this is a destructive inflammatory process, not excessive hormone production. 1

The appropriate management is:

• Observation with serial monitoring every 2-3 weeks to detect spontaneous resolution or transition to hypothyroidism 1
• Beta-blockers (atenolol or propranolol) only if symptomatic with palpitations, tremor, or anxiety 1
• Counsel that most cases resolve within weeks, often transitioning to a hypothyroid phase that may require levothyroxine 1, 2
• Monitor for transition to hypothyroidism with TSH and free T4 every 2-3 weeks, as approximately 20-40% develop permanent hypothyroidism within 3-10 years 2

If Graves' Disease (Less Common Postpartum)

Initiate thioamide therapy with propylthiouracil or methimazole to prevent progression to symptomatic disease and complications. 1

The treatment protocol is:

• Start methimazole or propylthiouracil at standard doses for asymptomatic biochemical hyperthyroidism 1
• Monitor FT4 or free thyroxine index every 2-4 weeks initially to adjust dosing 1
• Maintain FT4 in the high-normal range using the lowest effective thioamide dose 1
• Warn about agranulocytosis risk and instruct to report sore throat, fever, or signs of infection immediately 1

Critical Breastfeeding Considerations

• Both propylthiouracil and methimazole can be safely used during breastfeeding in moderately high doses without causing alterations in infant thyroid function 1
• Radioiodine therapy is absolutely contraindicated—women must not breastfeed for four months after I-131 treatment 1

Long-Term Monitoring Strategy

Women with highest TSH levels and anti-TPO antibodies during the hypothyroid phase require longer-term follow-up due to greatest risk of permanent hypothyroidism. 2

• Recheck thyroid function at 6 and 12 months postpartum even if initial hyperthyroid phase resolves 2
• Annual TSH screening thereafter for women with positive anti-TPO antibodies 2
• Screen for postpartum depression, as symptoms overlap with postpartum thyroiditis and affect 5-7% of women in the first year after delivery 3

Common Pitfalls to Avoid

• Do not start antithyroid drugs for postpartum thyroiditis—this is a self-limited destructive process, not Graves' disease 1
• Do not dismiss as "normal postpartum changes" without biochemical evaluation, especially in women with goiter or prior thyroid disease 1
• Do not assume permanent hypothyroidism—many women recover normal thyroid function after the transient hypothyroid phase 2
• Do not overlook the association with postpartum depression, as thyroid dysfunction and mood symptoms frequently coexist in the postpartum period 3