What is the management approach for a 14-week pregnant woman with hyperemesis gravidarum and Graves' disease in thyroid storm?

Management of Hyperemesis Gravidarum with Thyroid Storm in Pregnancy

Immediate Life-Threatening Priority: Thyroid Storm Management

This patient requires immediate aggressive treatment for thyroid storm without waiting for laboratory confirmation, using propylthiouracil (PTU), potassium/sodium iodide solutions, dexamethasone, beta-blockers, and supportive care, while avoiding delivery unless absolutely necessary. 1

Multi-Drug Regimen for Thyroid Storm

The treatment protocol must include all of the following components simultaneously:

• Start PTU immediately as the preferred thionamide at 14 weeks gestation, given its ability to inhibit peripheral conversion of T4 to T3, making it particularly effective for thyroid storm 1, 2

  • PTU is preferred over methimazole during first trimester due to lower risk of congenital abnormalities, and this patient is still in early second trimester 3
  • Do not delay treatment waiting for thyroid function tests—clinical diagnosis is sufficient 1

• Administer potassium or sodium iodide solutions at least 1 hour after starting PTU to block thyroid hormone release 1

  • The delay is critical to prevent iodine from being used as substrate for new hormone synthesis 1

• Give dexamethasone to block peripheral conversion of T4 to T3 and address potential relative adrenal insufficiency 1

• Administer intravenous beta-blockers aggressively (propranolol or esmolol) to control tachycardia and peripheral effects of thyroid hormone 1

  • High doses may be required in thyroid storm 1
  • Beta-blockers can be used temporarily until PTU reduces thyroid hormone levels 3

• Provide supportive care including IV fluids for dehydration, correction of electrolyte abnormalities, and cooling measures 3, 1

Critical Pregnancy-Specific Considerations

• Avoid delivery during thyroid storm unless absolutely necessary due to high maternal and fetal risk 3, 1
• Untreated thyroid storm poses severe risks including maternal heart failure, preeclampsia, preterm delivery, miscarriage, and fetal complications 1

Secondary Management: Hyperemesis Gravidarum

Distinguishing GTT from Graves' Disease

This clinical scenario requires careful differentiation between gestational transient thyrotoxicosis (GTT) and Graves' disease:

• GTT associated with hyperemesis gravidarum rarely requires antithyroid treatment unless other clinical signs of hyperthyroidism are present 3
• However, this patient has progressed to thyroid storm, which is a medical emergency requiring full treatment regardless of underlying etiology 3, 1
• Check for thyroid autoantibodies (TSH receptor antibodies, anti-TPO) to distinguish Graves' disease from GTT 4, 5
  • If antibodies are negative and hCG is markedly elevated, GTT is more likely 4, 5
  • GTT typically resolves spontaneously as hCG levels decline after first trimester 4, 5

HG-Specific Treatment

Once thyroid storm is stabilized, address the hyperemesis:

• IV fluid resuscitation to correct dehydration and electrolyte imbalances 6
• Antiemetic therapy with doxylamine (FDA-approved for NVP) and pyridoxine (vitamin B6, 10-25 mg every 8 hours) 6
• H1-receptor antagonists such as promethazine or dimenhydrinate as first-line pharmacologic antiemetics 6
• Nutritional support to prevent >5% weight loss and malnutrition 6
• Monitor for elevated liver enzymes (seen in 40-50% of HG patients) and vitamin deficiencies 6

Monitoring and Follow-Up

Acute Phase Monitoring

• Monitor free T4 or free thyroxine index (FTI) every 2-4 weeks once stabilized to guide PTU dosage adjustments 3, 1
• Goal is to maintain free T4 or FTI in the high-normal range using the lowest possible PTU dosage 3, 1
• Monitor for PTU side effects including agranulocytosis (sore throat, fever), hepatotoxicity, and vasculitis 3, 2

Medication Adjustment Strategy

• If GTT is confirmed (negative antibodies, elevated hCG, rapid improvement as hCG declines), antithyroid medications can likely be tapered and discontinued as symptoms resolve in second trimester 4, 5
• If Graves' disease is confirmed (positive antibodies), continue PTU through first trimester, then consider switching to methimazole for second and third trimesters given lower maternal hepatotoxicity risk 2
• In approximately 30% of Graves' patients, ATDs may be discontinued in the last few weeks of gestation 7

Fetal Monitoring

• Inform the newborn's physician about maternal thyroid condition due to risk of neonatal thyroid dysfunction 3
• Monitor fetal growth and heart rate 8
• PTU crosses placental membranes and can induce fetal goiter if excessive doses are used 2

Critical Pitfalls to Avoid

• Never use radioactive iodine (I-131) during pregnancy—it is absolutely contraindicated and causes fetal thyroid ablation 3, 1
• Do not delay treatment waiting for laboratory confirmation of thyroid storm—clinical suspicion is sufficient to begin therapy 1
• Do not give iodide solutions before PTU—wait at least 1 hour to prevent substrate for new hormone synthesis 1
• Do not routinely treat biochemical hyperthyroidism in HG with antithyroid drugs unless clinical signs of hyperthyroidism or thyroid storm are present 3
• Monitor prothrombin time before any surgical procedures as PTU may cause hypoprothrombinemia 2