Endocrine measurements in survivors and non-survivors from critical illness

Objective. To compare measurements of thyroid and adrenal function between survivors and non-survivors in critical illness. Design and setting. Prospective, observational study at the medical/surgical intensive care unit (ICU) at Royal Infirmary of Edinburgh, Scotland. Patients. 163 patients admitted to the intensive care unit over a 4-month period. Interventions. We took blood samples within 1 h of ICU admission, and at 08:00 hours on the subsequent 2 days of ICU admission. We measured serum total (TT 4 ) and free (fT 4 ) thyroxine, total (TT 3 ) and free (fT 3 ) tri-iodothyronine, thyrotropin (TSH) and plasma cortisol concentrations. Measurements and results. TT 3 and TT 4 concentrations were significantly less in non-survivors than in survivors on admission and on day 1 but not on day 2. Cortisol concentrations were higher in non-survivors on admission and on day 1 but not on day 2. TSH, fT 3 and fT 4 concentrations did not differ significantly between survivors and non-survivors at any time. Only TT 4 and cortisol were independent predictors of outcome. Prediction of outcome from the admission sample values was not better than using APACHE II scoring. Conclusions. Thyroid hormone and cortisol concentrations differ between survivors and non-survivors on admission to intensive care, but the values overlap. These differences do not allow accurate prediction of outcome from critical illness.