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Difficulty: Very hardGeneral Internal Medicine

An emergency medical services team brings a 68-year-old woman to the resuscitation bay in January due to progressive lethargy and generalized swelling over the past 48 hours. Two weeks ago, she experienced a mild upper respiratory tract infection. Her past medical history is notable for hypertension, hyperlipidemia, and a severe postpartum hemorrhage requiring multiple blood transfusions 38 years ago. Current medications include amlodipine and atorvastatin. Vital signs show a temperature of 34.2°C (93.6°F), blood pressure of 88/56 mm Hg, heart rate of 48/min, and respiratory rate of 8/min. Pulse oximetry is 90% on room air. Physical examination reveals a somnolent patient who only awakens to painful stimuli. Her face appears puffy with marked periorbital edema, and deep tendon reflexes exhibit significantly delayed relaxation. Lung fields are clear to auscultation.

Initial laboratory testing reveals the following:
Sodium: 124 mEq/L
Potassium: 4.1 mEq/L
Chloride: 92 mEq/L
Bicarbonate: 26 mEq/L

Arterial blood gas (room air):
pH: 7.24
PaCO2: 68 mm Hg
PaO2: 62 mm Hg

Thyroid-stimulating hormone (TSH): 1.5 mU/L (Normal: 0.5–5.0 mU/L)
Free T4: 0.3 ng/dL (Normal: 0.9–1.7 ng/dL)

Which of the following is the most appropriate next step in the management of this patient?

  1. Administer intravenous hydrocortisone prior to intravenous levothyroxineAnswer
  2. B
    Administer intravenous levothyroxine immediately to reverse the metabolic state
  3. C
    Administer an intravenous sodium bicarbonate infusion to rapidly correct the acidemia
  4. D
    Initiate non-invasive positive pressure ventilation and administer nebulized glycopyrrolate and arformoterol
  5. E
    Administer empiric intravenous cefepime and vancomycin alongside a rapid crystalloid bolus

Answer

Administer intravenous hydrocortisone prior to intravenous levothyroxine
The correct sequence of therapy requires recognizing that this patient has myxedema coma caused by panhypopituitarism, likely Sheehan syndrome, given her history of severe postpartum hemorrhage and a thyroid panel showing central hypothyroidism (low Free T4, normal TSH). Because central adrenal insufficiency is concurrently present, administering levothyroxine alone will accelerate the metabolic clearance of cortisol and provoke a fatal acute adrenal crisis. Intravenous hydrocortisone must be given first to provide stress-dose steroid coverage.

Step-by-Step Solution

1
Identify the clinical syndrome
The patient is presenting with myxedema coma, evidenced by profound hypothermia, bradycardia, altered mental status, delayed deep tendon reflexes, and non-pitting edema.
Recognizing the life-threatening extreme of hypothyroidism is required to initiate emergency endocrine resuscitation.
2
Analyze the acid-base and electrolyte status
The patient has severe hyponatremia and acute uncompensated respiratory acidosis (low pH, high PaCO2) driven by hypoventilation.
This confirms the severity of the myxedema coma and rules out primary metabolic causes for the acidemia.
3
Interpret the thyroid panel
The patient has a low Free T4 (0.3 ng/dL) with an inappropriately normal TSH (1.5 mU/L).
This laboratory pattern indicates central (secondary) hypothyroidism rather than primary hypothyroidism (where TSH would be markedly elevated).
4
Synthesize the endocrine history
The history of severe postpartum hemorrhage 38 years ago, combined with central hypothyroidism, points to Sheehan syndrome (postpartum pituitary necrosis) leading to panhypopituitarism.
Panhypopituitarism implies concurrent deficiencies in other pituitary hormones, most critically ACTH, resulting in central adrenal insufficiency.
5
Determine the pharmacological sequence
Intravenous hydrocortisone must be administered before or simultaneously with intravenous levothyroxine.
Administering thyroid hormone increases basal metabolic rate and hepatic clearance of cortisol. In a patient with untreated adrenal insufficiency, this will precipitate a fatal acute adrenal crisis.

Key Concept

In patients with suspected panhypopituitarism (e.g., Sheehan syndrome) presenting with myxedema coma, glucocorticoids must be administered before thyroid hormone replacement to avoid precipitating an acute adrenal crisis.
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Topics

General Internal Medicine

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