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Difficulty: HardPharmacologic Interventions

A 26-year-old primigravid woman at 9 weeks gestation is brought to the emergency department by her husband due to severe agitation, fever, and palpitations. She has been experiencing intractable nausea and vomiting for the past two weeks. On presentation, she is confused and restless. Temperature is 39.4∘C39.4^\circ\text{C} (102.9∘F102.9^\circ\text{F}), blood pressure is 150/65 mmHg150/65\text{ mmHg}, pulse is 148/min148/\text{min} and irregularly irregular, and respiratory rate is 24/min24/\text{min}. Physical examination reveals a diffusely enlarged, non-tender thyroid gland, a fine resting tremor, warm and moist skin, and hyperreflexia. Electrocardiogram confirms atrial fibrillation with rapid ventricular response. Laboratory studies show:

Thyroid-stimulating hormone (TSH): <0.01 \muU/mL<0.01\text{ \mu U/mL}
Free thyroxine (T4): 5.8 ng/dL5.8\text{ ng/dL} (Reference: 0.8−2.0 ng/dL0.8-2.0\text{ ng/dL})
Liver function tests: Within normal limits

Which of the following pharmacologic interventions should be included in the immediate management of this patient? (Select all that apply)

  1. Oral propylthiouracilAnswer
  2. Intravenous hydrocortisoneAnswer
  3. C
    Oral methimazole
  4. D
    Oral aspirin
  5. E
    Intravenous potassium iodide administered simultaneously with thionamides

Answer

The appropriate immediate interventions for this pregnant patient in thyroid storm are oral propylthiouracil and intravenous hydrocortisone.
The correct interventions are propylthiouracil and hydrocortisone. Propylthiouracil is the thionamide of choice during the first trimester of pregnancy to block the synthesis of new thyroid hormone and decrease peripheral conversion of T4 to T3, while avoiding the teratogenic risks of methimazole. Intravenous hydrocortisone is indicated to further reduce peripheral T4 to T3 conversion and provide coverage for relative adrenal insufficiency triggered by the hypermetabolic crisis.

Step-by-Step Solution

1
Diagnose the patient's acute condition based on clinical presentation and laboratory findings.
The patient has fever, tachycardia, agitation, a goiter, and markedly elevated free T4 with suppressed TSH, confirming a diagnosis of thyroid storm. She is also in her first trimester of pregnancy.
Accurate identification of both the endocrine emergency (thyroid storm) and the patient's specific physiological state (first trimester pregnancy) is essential to select safe and effective pharmacotherapy.
2
Select an antithyroid drug that is safe in early pregnancy to block hormone synthesis.
Propylthiouracil is selected over methimazole.
Propylthiouracil is preferred in the first trimester to avoid methimazole-induced embryopathy (e.g., aplasia cutis). It additionally blocks the peripheral conversion of T4 to T3.
3
Identify supportive pharmacotherapy to reduce active hormone levels and provide systemic support.
Intravenous hydrocortisone is selected.
Glucocorticoids inhibit peripheral deiodination of T4 to active T3 and treat potential relative adrenal insufficiency resulting from accelerated cortisol metabolism in thyroid storm.
4
Exclude contraindicated interventions that would worsen the thyrotoxicosis or harm the fetus.
Aspirin, methimazole, and simultaneous iodine administration are excluded.
Aspirin displaces T4 from binding proteins; methimazole is teratogenic in the first trimester; and iodine given before thionamide blockade fuels further hormone synthesis.

Key Concept

Management of Thyroid Storm in Pregnancy
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Topics

Pharmacologic Interventions

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