In critically ill patients, pronounced alterations in the hypothalamic-pituitary-thyroid axis occur without any evidence for thyroid disease. T3 decreases and rT3 increases within a few hours of the onset of disease. Severity and duration of disease are related to the magnitude of these changes. This manuscript discusses whether these changes in thyroid hormone levels during critical illness should be treated, and was in part published elsewhere.

Hypothalamic-pituitary-thyroid axis, Thyrotropin-releasing hormone, Thyroxine,
Annales d'Endocrinologie
Department of Internal Medicine

Peeters, R.P. (2007). Non thyroidal illness: to treat or not to treat?. Annales d'Endocrinologie, 68(4), 224–228. doi:10.1016/j.ando.2007.06.011