Crosstalk between thyroid dysfunction and kidney dysfunction in intensive care unit patients

This scientific review explores the intricate bidirectional relationship (crosstalk) between thyroid dysfunction and kidney dysfunction within the context of the intensive care unit (ICU). We discuss how critical illness and acute kidney injury (AKI) lead to thyroid dysregulation, specifically focusing on the high prevalence of non-thyroidal illness syndrome (NTIS) and low triiodothyronine (T3) levels in patients with renal impairment. Mechanisms such as altered deiodinase activity and selenium deficiency are highlighted. The article elucidates the impact of thyroid hormones on renal physiology: hypothyroidism is associated with reduced renal blood flow and glomerular filtration rate (GFR), potentially delaying AKI recovery, while hyperthyroidism induces glomerular hyperfiltration. Furthermore, we address the complexities introduced by renal replacement therapy (RRT), which can alter thyroid hormone kinetics. Recognizing this reciprocal interplay is crucial for intensivists to accurately interpret thyroid function tests and manage renal complications in critically ill patients.