Thyroid function changes and cytokine alterations following major surgery.

To establish whether cytokine release is implicated in thyroid hormone changes during surgical stress we studied 36 adult patients (20 men; mean age +/- SD: 68.5 +/- 10.5 years) undergoing elective major abdominal operations. We measured tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-8 and IL-10 and thyrotropin (TSH), free thyroxine (FT(4)) and triiodothyronine (T(3)) before scheduled non-emergency surgery, immediately postoperatively, on the 1st postoperative day (post-1) and on the 2nd postoperative day (post-2). TNF-alpha, IL-6 and IL-8 peaked on day post-1 whereas IL-10 peaked immediately postoperatively. Fourteen of 36 patients had low T(3) levels after surgery, indicating non-thyroidal illness (NTI). Significant negative correlations were noted among TNF-alpha, IL-6 and IL-8 against T(3) and FT(4). Cytokines are responsible, at least in part, for NTI following major operations.