Levothyroxine absorption and difficult management of hypothyroid patients in the intensive care unit: two case reports and a literature review.

Levothyroxine absorption in hypothyroid patients can be influenced by several factors, particularly medications and concomitant food administration. This is especially evident in intensive care unit patients, where a continual enteral diet and the administration of multiple medications changes its absorption. Changes or adaptations in the hypothalamic-pituitary-thyroid axis, in conjunction with clinical abnormalities possibly related to under-treatment of hypothyroidism, render levothyroxine replacement therapy very challenging. Here, we report two intensive care hypothyroidism patients and their respective levothyroxine replacement management issues, focusing on a number of controversial issues, such as the optimal replacement dose, how fast the levothyroxine doses should be increased, triiodothyronine requirements, the interference of an enteral diet with absorption, and finally, the possible consequences of undertreated hypothyroidism and levothyroxine replacement monitoring useful clinical/laboratory parameters.