Pituitary-thyroid function in patients with septic shock and its relation with outcome.

OBJECTIVE: To study the time course of thyroid function abnormalities and their relation to outcome in patients with septic shock. DESIGN: Prospective study in a cohort of consecutive patients. SETTING: Intensive Care Unit in a University Hospital. PATIENTS AND METHODS: We studied 27 patients (mean age 50 +/- 19 years, Apache II score 18.4 +/- 5.2, 15 survivors) diagnosed of septic shock. Total T4 (T4) and total T3 (T3) (RIA) were determined on days 1 and 5 after admission. We also measured TSH (ultrasensitive RIA) at 08.00, 20.00 and 01.00 hours (on days 1 and 5), and the TSH response to TRH (400 microg intravenous) on days 2 and 6. Data are mean +/- SD. RESULTS: Whereas low thyroid hormones concentrations were present on day 1 in all patients, only survivors presented a significant increase in T3 and T4 on day 5. Basal TSH levels and the area under the curve of the TSH response to TRH on day 2 were significantly higher in survivors than in non survivors (0.89 +/- 0.63 vs. 0.34 +/- 0.42 microIU/ml, and 229 + 157 vs. 101 + 101). The normal nocturnal (01.00 hr) surge of TSH (the difference between TSH concentrations at 8 am and at 1 am) was abolished in both survivors and non survivors on day 1 but it was recovered on day 5 only in survivors. CONCLUSIONS: Our data indicate that patients with septic shock present an altered hypothalamic-pituitary-thyroid axis, and that survivors thyroid function differs from that of non survivors shortly after diagnosis. Survivors are characterised by a greater TSH response to TRH, indicating a less deranged hypothalamic-pituitary-thyroid axis. Thyroid function improves in survivors, but not in non survivors, during the course of their illness.