We are proud to present CAPSULES module 7: Emergency Thyroid Disorders, now published on ALiEMU. Here is a summary of the key points from this outstanding module by Drs. Craig Cocchio and Colleen Martin.
|Authors||Craig Cocchio, PharmD, BCPS @iEMPharmD||Emergency Medicine Pharmacist, Trinity Mother Frances Hospital|
|Colleen Martin, PharmD, BCPS||Emergency Medicine Pharmacist, Nyack Hospital|
|PharmD Reviewer and Associate Editor||Nadia Awad, PharmD, BCPS @Nadia_EMPharmD||Emergency Medicine Pharmacist, Robert Wood Johnson University Hospital|
|Physician Reviewer||George Willis, MD @DocWillisMD||Assistant Professor of Emergency Medicine, University of Maryland|
|Copy Editor||Meghan Groth, PharmD, BCPS
|Emergency Medicine Pharmacist, University of Vermont Medical Center|
|Creator and Lead Editor||Bryan Hayes, PharmD, FAACT@pharmertoxguy||Emergency Medicine Pharmacist, Massachusetts General Hospital|
|Chief of Design and Development and Co-Founder of ALiEMU||Chris Gaafary, MD@cgaafary||Clinical Assistant Professor, Greenville Health System|
Go to ALiEMU module
Summary: Emergency Thyroid Disorders
Thyroid disorders and their emergencies are a challenge to recognize in the clinical setting, offer few evidence-based treatment options and are associated with a high incidence of morbidity and mortality. This CAPSULE will help the reader digest the critical aspects of the pharmacotherapy of these emergencies and provide a springboard into deeper learning through the vast resources of primary literature, textbooks and FOAM. This preview (or loading dose, if you will) highlights a few key CAPSULES in this module.
As part of the hypothalamic-pituitary-thyroid axis, the thyroid gland plays critical roles in numerous metabolic processes. The hormones; thyroxine (T4), triiodothyronine (thyronine, or T3), and calcitonin, are critical in both the development and ongoing function of almost every organ system. As a result, derangements in thyroid function can elicit broad non-specific signs and symptoms. However, thyroid disorders may exist on a spectrum including hypo- and hyperthyroid states may elicit manifestations of medical emergencies that may require extreme pharmacologic interventional measures.
Presentation of myxedema coma & thyroid storm may mimic sepsis
The most concerning extreme form of hypothyroidism is myxedema coma. Myxedema coma is, however, a medical misnomer. While referring to a state of decompensated hypothyroidism (DH), myxedema coma does not always involve myxedema (nonpitting edema) or coma. DH presents as an exaggeration of hypothyroid effects; altered mental status, hypothermia, hypotension, hypoventilation, hypoglycemia and hyponatremia.
These widespread generalized signs and symptoms make DH difficult to recognize, but the combination of hypotension, hypothermia, altered mental status should alert clinicians to consider DH.
Levothyroxine (IV or PO) is the drug of choice in acute management of DH.
Thyroid hormone replacement
Ultimately, the goal of treatment once DH is identified is replacement of thyroid hormones. The three categories that have been described include intravenous (IV) T4, oral (PO) T4, and combination therapy with IV/PO T4 and IV/PO T3. The absence of high quality evidence precludes one therapy over another being determined as first line. Thus, treatment recommendations may be based upon consensus or clinician experience.
Oral loading doses of levothyroxine should be double the desired IV loading dose.
Oral loading of levothyroxine has been suggested as an option, particularly in areas where IV levothyroxine is not available. Some references cite low (<50%) bioavailability of levothyroxine oral tablets, modern oral dosage forms of levothyroxine may have a bioavailability of closer to 80%. Despite this, the IV to oral conversion for levothyroxine loading doses should remain as 1:2 since in this clinical scenario, this conversion is not intended to be the final dose but rather a starting point from which the dose will be titrated to desired free T4 and TSH.
Hyperthyroidism is characterized by increased production and release of thyroid hormone by the thyroid gland and can present in a wide spectrum, from sub-clinical, to life-threatening. Thyrotoxicosis is present when there are elevated levels of thyroid hormone in the blood, which may be present in the absence of hyperthyroidism if thyroid hormone is caused by extrathyroidal sources of hormone or release of preformed thyroid hormone. Thyroid storm, or thyrotoxic crisis, occurs when thyrotoxicosis becomes life-threatening.
Management of thyroid storm should begin immediately due to its reported mortality of 8 – 25%. Treatment of thyroid storm includes all of the following:
- Antiadrenergic therapy
- Suppression of thyroid hormone formation and secretion
- Preventing peripheral conversion of thyroid hormone
- Treatment of associated complications or coexisting factors that may have precipitated the storm
- Supportive therapy
Propylthiouracil is preferred over methimazole in pregnancy
Suppressing the amount of thyroid hormone in systemic circulation is important in reversal of thyroid storm. The first-line treatment is the use of thionamides which inhibit thyroid peroxidase, the enzyme required for thyroid hormone synthesis. Methimazole and propylthiouracil can be administered rectally if the oral route is not feasible as a retention enema.
Thionamide (propylthiouracil or methimazole) should be given prior to iodine
One hour after the administration of a thionamide, iodine should be administered to prevent the release of thyroid hormones. The time delay is recommended so that the thionamide has had a chance to prevent synthesis of thyroid hormone before providing a large dose of substrate that could used to synthesize additional thyroid hormones.
What is the CAPSULES series?
CAPSULES is a free, online e-curriculum of high-quality, current, and practical pharmacology knowledge for the EM practitioner. About once a month a new course module is released, which has lessons to read about (or watch) and brief quizzes to complete. With each step, your personal dashboard will keep track of what you have completed. The CAPSULES series’ primary focus is bringing EM pharmacology education to the bedside. Our expert team distills complex pharmacology principles into easy-to-apply concepts. It’s our version of what-you-need-to-know as an EM practitioner.