Management of severe hypothyroidism and myxedema coma

Dr Leonard Wartofsky is a professor of medicine at Georgetown University Hospital, chairman emeritus of the Department of Medicine at the Washington Hospital Center, and past president of the American Thyroid Association and the Endocrine Society.

What is the appropriate treatment in patients with severe hypothyroidism and myxedema coma? What thyroid hormones should be administered (T₄ and T₃ administered together or separately)? What dosing should be used?

Leonard Wartofsky, MD, MPH: Patients with myxedema require a very tight control of their ventilatory status—again, we are talking about intensive care (ICU) management of their ventilation and cardiovascular system. They have bradycardia and can have other rhythm disturbances, so these need to be monitored closely while administering therapy. They are hypothermic, so they need warming blankets, but not electric warming blankets. They need to be warmed slowly. Too rapid warming will lead to peripheral dilatation, a drop in blood pressure, and potential shock. They may have reduced blood volume and reduced cardiac output, so careful attention to fluid management is important as well.

For the specific therapy, thyroid hormone is required—either thyroxine (T₄) or triiodothyronine (T₃), or both. I am an advocate of giving both, and the reason for both is that these patients are typically sick and do not normally convert T₄ to T₃, and T₃ is the active thyroid hormone. In order to really turn this event around from a catastrophe to potential recovery you need the action of thyroid hormone quickly, and that can only be achieved through T₃.

Doses of T₄ are given to provide a pool of hormone to then be acted upon for the slow conversion to T₃, and that dose can be anywhere from 200 to 500 microg of thyroxine given intravenously (IV) as a bolus dose. That is followed by doses of T₃ of 20 to 60 microg as an IV bolus, with repeat dosage in approximately 12 hours of half that amount, monitoring the patient for rhythm disturbances and blood pressure.