Efficacy and Pharmacokinetics of Oral Thyroid Replacement Therapy in Organ Donors

Disruption of the hypothalamic-pituitary axis following brain death may lead to hemodynamic instability, peripheral vasodilation, and diabetes insipidus in organ donors, requiring the use of high doses of inotropes. Inotropes may cause ischemic injury to organs and intramyocardial ATP stores, resulting in organs unsuitable for transplantation, as well as, a reduction in post-transplant organ function. Therefore, some clinicians advocate the use of triple hormonal therapy in potential organ donors.

Since intravenous T3(the intracellular active form of thyroxine) is unavailable, oral or intravenous T4 must be used, requiring the conversion of T4 to T3at the cellular level. This conversion is impeded by glucocorticoids which also are administered to organ donors for their immunomodulating effects. Since oral T3 is readily available, our first question is whether oral versus intravenous administration of T4 is comparable. If so, our next study is to determine the efficacy of oral T3 versus oral T4. Our hypothesis is oral T3 is superior to oral T4.

Our study therefore will determine whether or not the oral route is suitable for administration of thyroid replacement therapy. The study will compare the pharmacokinetics of oral versus intravenous T4 administration in organ donors, as well as, determine its ability to wean intropes in this patient population.