Hypothyroidism, Emergency Medicine

Basics

Description

Decreased level of effective circulating thyroid hormone leads to decreased metabolic rate and decreased sensitivity to catecholamines.
More common in woman and the elderly
Myxedema coma is a rare, extreme form of hypothyroidism characterized by altered mental status and defective thermoregulation triggered by a precipitating event in a patient with hypothyroidism.

Etiology

Primary:
- Idiopathic
- Congenital
- Autoimmune:
  - Thyroiditis
  - Hashimoto disease
- Iatrogenic:
  - Postsurgical
  - External radiation
  - Radioiodine therapy
  - Drugs (iodides, lithium, amiodarone, sunitinib, bexarotene, interferons, narcotics, sedatives)
- Neoplasm: Primary (carcinoma) or secondary (infiltration)
- Infection: Viral (rarely aerobic or anaerobic bacteria)
- Iodine deficiency (most common cause worldwide)
Central (very rare):
- Pituitary or hypothalamic disorder induced by drugs or severe illness
- May have other associated hormone deficiencies
Myxedema coma:
- Critical decompensation of a patient with hypothyroidism due to a stress, often during winter months. Stressors include:
  - Infection
  - Hypothermia
  - Intoxication
  - Drugs
  - Cerebrovascular accident
  - Heart failure
  - Trauma

Hypothyroid women require increased exogenous thyroid hormone replacement during pregnancy above baseline
Postpartum thyroiditis occurs in up to 10% of women:
- Usually 3-6 mo postpartum
- Typically resolves without treatment

Diagnosis

Signs and Symptoms

History

Exhaustion
Cold intolerance
Headaches
Diminished hearing
Myalgias and muscle weakness
Menorrhagia
Infertility
Carpal tunnel syndrome
Constipation
Weight gain
Depression, hallucinations, or paranoia
Cognitive impairment

Physical Exam

Periorbital edema
Sparse, coarse hair and brittle nails
Absent lateral 1/3 of eyebrows (Queen Anne sign)
Husky or hoarse voice
Goiter
Prolonged relaxation phase of deep tendon reflexes (DTRs)
Yellow, dry, pale, cool, coarse skin
Myxedema (dry, waxy swelling of skin)
Nonpitting edema of hands and feet
Myxedema coma:
- Altered mental status
- Hypotension
- Hypothermia
- Respiratory failure
- Bradycardia

Undiagnosed hypothyroidism in infants has largely been eliminated via universal screening at birth
Hypothyroidism in childhood is usually due to Hashimoto disease.
Children may manifest with retardation of mental developmental, linear growth, and sexual maturation

Typical symptoms of hypothyroidism may be confused with changes associated with aging.

Essential Workup

Lab confirmation of the diagnosis of hypothyroidism/myxedema coma may not be available in the ED, and therapy should be initiated based on clinical suspicion.

Diagnosis Tests & Interpretation

Search for the underlying cause of myxedema coma.
Lab

Thyroid function studies:
- Low total and free thyroxine (T4)
- Low total and free triiodothyronine (T3)
- Thyroid stimulating hormone (TSH):
  - Increased in primary hypothyroidism but normal or decreased in central pathology
Anemia
Hyponatremia
Hypoglycemia
Hypoxemia
Hypercapnia
Respiratory acidosis
Elevated lactate dehydrogenase (LDH), creatine kinase (CK), cholesterol, creatinine

Imaging
CXR:

Enlarged cardiac silhouette due to pericardial effusion

Diagnostic Procedures/Surgery
ECG:

Sinus bradycardia, low voltage, PR interval prolongation, bundle branch blocks, QT interval prolongation and nonspecific ST-T-wave changes
May see Osborn wave if profoundly hypothermic

Differential Diagnosis

Chronic nephritis
Chronic renal disease
Heart failure
Depression
Hypoalbuminemia
Pernicious anemia
Nephrotic syndrome
Sepsis

Euthyroid sick syndrome:
- Illness, surgery, fasting may produce abnormal thyroid function test results
- Thyroid function tests performed during acute nonthyroid illness may be abnormal and should be interpreted with caution

Treatment

Initial Stabilization/Therapy

ABCs:
- Intubation and ventilation may be necessary
Cardiac monitor
Blood pressure support
Supplemental oxygen to meet metabolic needs
Correct hypothermia:
- Initiate passive warming measures
- Aggressive rewarming may precipitate hypotension from vasodilation

Ed Treatment/Procedures

Mild hypothyroidism:
- Refer for oral thyroid hormone replacement as an outpatient
Myxedema coma:
- Life-threatening condition
- Initiate thyroid hormone replacement therapy if a high index of suspicion:
  - Prompt IV replacement improves survival
  - Controversy over regimen exists
  - Thyroxine (T4) and triiodothyronine (T3)
  - Reassess 4 hr after initial dose
  - Use smaller doses of T4 and avoid T3 in the elderly or patients with cardiac disease to avoid precipitating ischemia
- Hydrocortisone to prevent Addisonian crisis
- Dextrose for hypoglycemia
- IV fluid bolus for hypotension:
  - Avoid pressors if possible, may precipitate dysrhythmias
  - Response to pressors is poor until thyroid replacement initiated
  - Thyroid hormone augments pressors
- Consider hypertonic saline for severe hyponatremia
- Correct the underlying precipitant

Medication

First Line
Thyroid hormone therapy:

Administer T4, T3, or a combination:
- Combination therapy:
  - Thyroxine (T4): 2 Î¼g/kg (ideal body mass) load IV followed by 10-40 Î¼g IV/PO daily
  - PLUS
  - Triiodothyronine (T3): 10 Î¼g load IV followed by 10 Î¼g IV q8-12h until able to tolerate PO T4
- Thyroxine (T4): 10-40 Î¼g IV or IM daily
- Triiodothyronine (T3): 10-20 Î¼g load IV followed by 10 Î¼g IV q4h for 24 hr, then 10 Î¼g IV q6h for 24-48 hr

Second Line

Hydrocortisone: 100 mg (peds: 4 mg/kg/24h) IV q6-8h
Dextrose: 50-100 mL D50 (peds: 5 mL/kg of D10) IV

Follow-Up

Disposition

Admission Criteria
All patients with myxedema coma require ICU admission.
Discharge Criteria
Hypothyroidism is managed in the outpatient setting.
Issues for Referral

Primary care providers can generally manage hypothyroidism.
Pregnant patients, elderly patients, and those with ischemic heart disease require special consideration when initiating thyroid hormone replacement.

Follow-Up Recommendations

Patients should be referred to a primary care provider for initiation of oral thyroid hormone replacement therapy.
Severe untreated maternal hypothyroidism can negatively impact fetal brain development and cause obstetrical complications.

Pearls and Pitfalls

Signs and symptoms of hypothyroidism are nonspecific and may be confused with other mental or physical disorders.
Response to treatment for hypothyroidism may take weeks and is best initiated by the primary care physician.
Consider myxedema coma in patients with altered mental status and underlying hypothyroidism.
Myxedema coma has a high mortality rate and requires aggressive treatment. However, avoid parenteral T3 in cardiac and elderly patients.

Additional Reading

Brent GA, Davies TF. Hypothyroidism and thyroiditis. In: Melmed S, Polonsky KS, Larsen PR, et al. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Saunders Elsevier; 2011:Chapter 13.
Klubo-Gwiezdzinska J, Wartofsky L. Thyroid emergencies. Med Clin North Am. 2012;96(2):385-403.
Mathew V, Misgar RA, Ghosh S, et al. Myxedema coma: A new look into an old crisis. J Thyroid Res. 2011;2011:493462.
Vaidya B, Pearce SH. Management of hypothyroidism in adults. BMJ. 2008;337:a801.

Codes

ICD9

243 Congenital hypothyroidism
244.8 Other specified acquired hypothyroidism
244.9 Unspecified acquired hypothyroidism
244.0 Postsurgical hypothyroidism
244.1 Other postablative hypothyroidism
244.2 Iodine hypothyroidism
244.3 Other iatrogenic hypothyroidism
244 Acquired hypothyroidism
245.2 Chronic lymphocytic thyroiditis

ICD10

E03.1 Congenital hypothyroidism without goiter
E03.5 Myxedema coma
E03.9 Hypothyroidism, unspecified
E89.0 Postprocedural hypothyroidism
E03.2 Hypothyroidism due to meds and oth exogenous substances
E03.8 Other specified hypothyroidism
E06.3 Autoimmune thyroiditis

SNOMED

40930008 Hypothyroidism (disorder)
43153006 Myxedema (disorder)
190268003 Congenital hypothyroidism (disorder)
27059002 Postoperative hypothyroidism
190279008 Iodine hypothyroidism (disorder)
237527007 Postablative hypothyroidism (disorder)

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