223. Thyroid Disorders: Hypothyroidism and Myxedema Crisis

Hypothyroidism

High TSH, low free T4/T3.

No perfect thyroid test. TSH is monitoring pituitary T3. Accurate only under ideal health. Free T4 is likely better test with TSH is the new state. Hypothyroid is a clinical diagnosis. (USC Rounds, 2017)

Causes: Autoimmune (Hashimoto), Thyroiditis (subacute, silent, postpartum), ablation, Drugs (amiodarone, lithium, alpha-Interferon, interleukin-2).

Symptoms: weight gain, weakness, fatigue, vocal changes (hoarse/deep), delayed DTRs, non-pitting edema (myxedema – periorbital, nondependent areas), paresthesias, poor memory/confusion, constipation, dysfunctional uterine bleeding. 5% of carpal tunnel patients have it.

Low voltage EKG.

Hypothyroidism usually cannot produce WBC. Usually 3-4k, lymphocytic predominant. If higher around 8-10k, really consider infection.

Initial ED Management with simple hypothyroidism: Likely discharge with followup with PCP for outpatient workup/treatment.

Myxedema Coma/Crisis

Extreme presentation of hypothyroidism. High mortality, life-threatening. Misleading name: usually not myxedema apparent, rarely in coma.

90% are women in winter months. Usually elderly > 60yo.

Clinical diagnosis. Altered (some big degree of AMS), hypothermia, body habitus for hypothyroidism. Usually bradycardia, hypotension, hypothermia. Stressor involved: infection (MCC), trauma, MI/CHF, surgery, medications, etc. Usually does not have a temperature and if has a normal temperature, have high suspicion for infection. Pleural effusions can be present. Look for thyroidectomy scar in altered patient. Usually hyponatremia. CPK almost always > 500.

Treatment

Supportive care: usually dehydrated, passive warming with warming blankets, vasopressors if unresponsive to fluids. ICU admission.

Usually adrenal insufficiency involved so give hydrocortisone 100mg q8h before thyroid medication. Send random cortisol level before doing this if able.

Start with T4 over T3. Smooth/gradual rise, no high peaks and increased potential for arrhythmias/MI as T3. T3 though has advantage of quicker onset and no potential for decreased peripheral conversion (T4 to T3), though usually not recommended over T3. T4 500mcg or 200-400mcg (4mcg/kg) IV bolus, then 100mcg daily after that. Likely just stick with T4 only. If you’re going to give T3 (probably stay away from), give T3 5-20mcg IV bolus or consider giving very small bolus of T3 along with T4 if you really want to give T3 as well. Since body is converting T4 to T3, with giving a high dose of T4, the body will adjust to convert the appropriate amount to T3 so pretty safe to give high dose T4 (not T3 though). IV dose still takes around 12 hours before HR response.

Give antibiotics regardless of if theres an apparent infection initially since the myxedema coma masks many of the signs of infection.


References / Resources

Tintinalli, 7th Edition, Chapter 223: Thyroid Disorders: Hypothyroidism and Myxedema Coma

CrashingPatient.com, Scott Weingart, Thyroid Disorders, Reviewed 11/6/15 (FREE)

EBMedicine, Identifying and Treating Thyroid Storm and Myxedema Coma in the ED, 2009 (FREE)

EMRAP, Stuart Swadron / John LoPresti, Severe Hypothyroidism, 2010

WikiEM, Myxedema Coma (FREE)


Clinical Cases


Board Questions

Q1. Which type of patient is most characteristic to be in myxedema coma?

A1. Elderly woman with pneumonia in January. Incorrect answers: Dehydrated marathon runner, Male with MI that he presented 3-4 days later, Obese young female collapses and comes in unresponsive by EMS, etc.

Q2. Which drug does not cause affect the thyroid and can cause hypothyroidism?

A2. Droperidol. Incorrect answers: Lithium, Amiodarone, Phenytoin, All the above.

Q3. With a patient in myxedema coma from a MI/CHF, which medication should be given?

A3. T4. Incorrect answers: T3, Amiodarone, Beta-blocker, All the above.

Q4. Besides T4 and supportive measures, what other medication should be likely given with severe myxedema coma?

A4. Hydrocortisone. Incorrect answers: Amiodarone, Beta-Blocker, Methamazole, etc.

Q5. Whats the most common EKG finding in myxedema coma?

A5. Sinus bradycardia. Incorrect answers: Slow atrial fibrillation, bigimeny, ventricular tachycardia, second degree heart block, etc.

Q6. What lab abnormality is usually present with myxedema coma?

A6. Elevated CPK. Incorrect answers: Significant leukocytosis, hypernatremia, positive HCG, etc.

223. Thyroid Disorders: Hypothyroidism and Myxedema Crisis