A 32-year-old postpartum woman, four months after delivery of her second child and currently breastfeeding, presents with daily episodes of nausea and dizziness; what should the diagnostic workup include?

Workup for Postpartum Nausea and Dizziness

Begin with thyroid function testing (TSH and free T4) as the primary diagnostic step, since postpartum thyroid dysfunction occurs in up to 10% of pregnancies and presents with these exact symptoms at 1-6 months postpartum. 1

Initial Laboratory Evaluation

Essential first-line tests:

• TSH and free T4 - Postpartum thyroiditis classically presents at 1-6 months postpartum with thyrotoxicosis (causing nausea, dizziness) followed by hypothyroidism 1
• Complete blood count (CBC) - Assess for anemia from postpartum blood loss
• Basic metabolic panel - Check sodium (severe hyponatremia can present with nausea and dizziness in postpartum women with pituitary pathology) 2, 3
• Blood glucose - Rule out hypoglycemia or diabetes-related complications

Thyroid-Specific Workup

If TSH is abnormal:

• TPO antibodies - Women with positive TPO antibodies are 27 times more likely to develop postpartum thyroiditis 1
• TRAb (TSH receptor antibodies) - Distinguish postpartum thyroiditis from Graves' disease recurrence, as higher titers suggest Graves' disease 1

Key distinction: Postpartum thyroiditis is self-limited and requires only symptomatic treatment with beta-blockers (propranolol preferred in breastfeeding), while Graves' disease requires antithyroid drugs 1

Secondary Considerations

If thyroid function is normal, evaluate:

• Blood pressure measurement - Postpartum preeclampsia can develop de novo up to 6 weeks postpartum, presenting with headache, visual changes, and nausea 4
• Morning cortisol (8 AM) - Pituitary infarction (Sheehan's syndrome) can occur without obvious hemorrhage and presents with nausea, fatigue, and failure to lactate 2, 3

Red Flag Symptoms Requiring Urgent Evaluation

Immediate workup if present:

• Severe headache with visual changes → Brain MRI to rule out pituitary pathology 2
• Chest pain, severe dyspnea, or orthopnea → ECG, troponin, BNP for postpartum cardiomyopathy 5, 6
• Fever with abdominal pain → Evaluate for endometritis 6
• Failure to lactate → Suggests hypopituitarism 2, 3

Clinical Pitfalls

Common diagnostic errors:

• Attributing all postpartum symptoms to "normal postpartum changes" - 32% of postpartum thyroiditis cases present with thyrotoxicosis alone without subsequent hypothyroidism 1
• Missing hyponatremia - Always check electrolytes as severe hyponatremia from pituitary pathology can present subtly 2, 3
• Overlooking cardiovascular causes - Postpartum cardiomyopathy typically presents 1-5 months postpartum with nonspecific symptoms 5, 6

Breastfeeding Considerations

If thyrotoxicosis is confirmed:

• Beta-blockers (propranolol or metoprolol) are safe during breastfeeding with minimal breast milk excretion 1
• Avoid radioactive iodine studies (I-131) - Use technetium-99m or I-123 if imaging needed, allowing breast milk to be pumped and discarded 1

Timeline-Based Approach

At 4 months postpartum, the differential diagnosis prioritizes:

1. Postpartum thyroiditis (peaks at 1-6 months) - Most likely 1
2. Postpartum cardiomyopathy (1-5 months typical) 5, 6
3. Pituitary pathology (can present weeks to months postpartum) 2, 3
4. Anemia (ongoing from delivery)