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Increasing thyroid dysfunction is associated with more serious illness and mortality in patients in intensive-care units
The background of the study. Many patients with nonthyroidal illness have abnormal serum thyroid hormone and thyrotropin (TSH) concentrations, and the frequency and severity of the changes increase in proportion to the severity of the illnesses. In this study, pituitary–thyroid function was assessed in patients admitted to an intensive-care unit (ICU), and the results correlated with severity of illness and other outcomes.
How the study was done. Serum free triiodothyronine (T3), free thyroxine (T4), and TSH were measured in 220 patients (average age, 59 years) soon after admission to an ICU. The Acute Physiology and Chronic Health Examination II (APACHE II) score (an indicator of severity of illness) was calculated soon after admission and the main diagnoses were recorded. The average stay in the unit was 10 days, during which 122 (49 percent) required mechanical ventilation and 45 (18 percent) died.
The results of the study. Seventy-nine patients (36 percent) had normal serum free T3, free T4, and TSH concentrations (euthyroid group), and 97 (44 percent) had low serum free T3 concentrations. Among the latter, 52 (24 percent) had normal serum TSH concentrations, 45 (20 percent) had low serum TSH concentrations, and 24 (11 percent) had low serum free T4 concentrations.
The APACHE II score, duration of ICU stay, and need for mechanical ventilation were lowest in the euthyroid patients and highest in the patients with low serum free T3 and free T4 values (Table).
| Table. Mean APACHE II Score, Length of ICU Stay, and Need for Mechanical Ventilation in Relation to Serum Free T3, Free T4, and TSH Concentrations Soon after Admission in 220 ICU Patients. | ||||
No. |
APACHE II Score |
ICU Stay (days) |
Mechanical Ventilation (no.) |
|
| Normal | 79 |
12.5 |
3 |
35(44%) |
| Low serum free T3 | 97 |
18 |
5 |
48(50%) |
| Low serum free T3 and free T4 | 24 |
21 |
13 |
20(83%) |
The ICU mortality rate was 13 percent in the euthyroid patients, 18 percent in the patients with low serum free T3 concentrations, and 46 percent in the patients with low serum free T3 and free T4 concentrations.
The conclusions of the study. Illness severity, length of stay, and mortality were higher in patients in the ICU who had low serum free T3 and free T4 concentrations than in those who had low or normal serum free T3 concentrations.
The original article. Plikat K, Langgartner J, Buettner R, Bollheimer LC, Woenckhaus U, Scholmerich J, Wrede CE. Frequency and outcome if patients with nonthyroidal illness syndrome in a medical intensive care unit. Metabolism 2007;56:239-44.
| Thyroid Digest Index | | | March 2007 Thyroid Digest |
