Internal Medicine · Year 3 · from Internal Medicine

Case 2: Myxedema Coma

Patient Demographics

  • Age: 76 years
  • Sex: Female
  • Occupation: Retired nurse

Chief Complaint

Found unresponsive at home by her daughter.

History of Present Illness

The patient was found unresponsive in her home by her daughter who came to check on her after not hearing from her for 2 days. The home was very cold as the heating had malfunctioned. The daughter reports that her mother has a history of hypothyroidism diagnosed 15 years ago and was on levothyroxine, but she ran out of medication approximately 2 months ago and did not refill it due to financial difficulties. Over the past several weeks, the patient had become increasingly fatigued, constipated, and "slow in her thinking" according to family members. The daughter last spoke with her 3 days ago when she was complaining of a "cold" with cough and congestion.

Vital Signs

  • Temperature: 93.2 degrees F (34.0 degrees C) - hypothermia
  • Blood pressure: 84/58 mmHg - hypotension
  • Heart rate: 42 bpm - bradycardia
  • Respiratory rate: 8/min - hypoventilation
  • Oxygen saturation: 86% on room air

Physical Examination

General: Obtunded, responds only to painful stimuli, non-pitting edema of face and extremities (myxedema) HEENT: Periorbital edema, macroglossia, coarse dry hair, lateral eyebrow thinning Neck: Thyroidectomy scar noted, no palpable thyroid tissue Cardiovascular: Bradycardic, distant heart sounds, no murmurs, JVP difficult to assess Pulmonary: Shallow respirations, decreased breath sounds at bases, dullness to percussion bilaterally Abdomen: Distended, hypoactive bowel sounds Extremities: Non-pitting edema, delayed relaxation of deep tendon reflexes, cool dry skin Neurologic: GCS 7 (E1V2M4), responds only to painful stimuli

Laboratory Findings

  • TSH: 127 mIU/L (markedly elevated)
  • Free T4: < 0.1 ng/dL (undetectable)
  • Free T3: < 0.5 pg/mL (undetectable)
  • Sodium: 118 mEq/L (low - hyponatremia)
  • Glucose: 52 mg/dL (low - hypoglycemia)
  • Cortisol (random): 8 mcg/dL (low-normal, inadequate for stress)
  • ABG: pH 7.28, PaCO2 58 mmHg, PaO2 54 mmHg (respiratory acidosis with hypoxemia)
  • CPK: 2,840 U/L (elevated)
  • Hemoglobin: 9.8 g/dL (anemia)

Chest X-ray

  • Bilateral pleural effusions
  • Enlarged cardiac silhouette (pericardial effusion versus cardiomegaly)

Diagnosis

Myxedema coma secondary to severe hypothyroidism from medication non-adherence, precipitated by cold exposure and presumed respiratory infection

Management

Airway and breathing:

  1. Endotracheal intubation for airway protection and respiratory failure
  2. Mechanical ventilation with careful attention to avoid hyperventilation

Thyroid hormone replacement:

  1. IV levothyroxine (T4) 200-500 mcg loading dose (use lower end of range given age and cardiac risk)
  2. Continue IV levothyroxine 50-100 mcg daily until able to take PO
  3. Consider adding IV liothyronine (T3) 5-20 mcg every 8 hours for faster onset (controversial)

Glucocorticoid coverage:

  1. Hydrocortisone 100 mg IV every 8 hours
  • MUST give before or with thyroid hormone to prevent precipitating adrenal crisis
  • Thyroid hormone replacement increases cortisol metabolism
  • Can discontinue after adrenal insufficiency is excluded by cosyntropin stimulation test

Supportive care:

  1. Passive rewarming with blankets (avoid active external warming which causes vasodilation and cardiovascular collapse)
  2. IV dextrose for hypoglycemia
  3. Careful IV fluid resuscitation (these patients have impaired free water excretion)
  4. Treat precipitating infection with broad-spectrum antibiotics
  5. ICU admission with continuous cardiac monitoring

Avoid:

  • Sedatives and opioids (impair already depressed respiration)
  • Active external warming
  • Rapid fluid resuscitation (risk of fluid overload with cardiac dysfunction)

Clinical Pearl

Myxedema coma represents the most severe manifestation of hypothyroidism and carries a mortality rate of 30-60% even with treatment. The hallmark clinical triad is hypothermia, altered mental status, and a precipitating event (often infection or cold exposure). Unlike its name suggests, true coma is not required for diagnosis - any degree of altered mentation in the setting of severe hypothyroidism should trigger concern. The most critical management principle is that glucocorticoids MUST be administered before or concurrent with thyroid hormone replacement, as thyroid hormone increases cortisol metabolism and can precipitate adrenal crisis in patients with subclinical adrenal insufficiency.

Clinical Image

Image Description: Clinical photograph demonstrating features of thyroid disease affecting the neck region. In myxedema coma, patients may show non-pitting edema of the face and extremities, but the thyroid gland itself may be atrophic (as in Hashimoto's thyroiditis) or absent (post-thyroidectomy).

Attribution: Image from Wikimedia Commons, by Michael Starks. Licensed under CC BY-SA 3.0. Source: https://commons.wikimedia.org/wiki/File:Goitre_-_Teknaf%2C_Bangladesh.jpg

All cases for this lecture as Markdown