The primary aim of the study would be to determine whether there is a difference in survival in the Intensive Care Unit between the group of patients with septic shock diagnosed with euthyroid sick syndrome who were treated with T3 hormone compared to the group of patients not treated with this hormone. Secondary objectives of the research would be:

Compare the level of thyroid hormones between the examined groups and

1. laboratory indicators of septic shock (C-reactive protein-CRP, procalcitonin, leukocytes, acid-base status, lactates)
2. APACHE II, SOFA and SAPS II patient assessment scales,
3. inflammatory prognostic systems (ratio of CRP and albumin-modified Glasgow prognostic score-mGPS, ratio of neutrophils and lymphocytes - NLR, ratio of platelets and lymphocytes - PLR, and ratio of leukocytes and CRP, prognostic index - PI)
4. hemodynamic stability of patients (MAP, systolic and diastolic pressure) in the periods of admission T0, T3, T6, T12, T24 and every 24 hours for 4 days,
5. effect of vasoactive drugs,
6. the need for mechanical ventilation categorized as yes or no, in case - number of respirator days,
7. length of stay in the Intensive Care Unit,
8. treatment outcome categorized as 28 day survival.

Inclusion Criteria:

• all patients who meet the criteria for septic shock according to the definition of Surviving sepsis campaigning (The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA 2016): persistent hypotension requiring the use of vasoactive drugs to maintain mean arterial pressure ≥65 mm Hg ; blood lactates> 2 mmol / L despite adequate resuscitation volume,
• patients with laboratory-proven euthyroid sick syndrome, according to diagnostic criteria which include: normal levels of TSH hormone, low levels of T3 hormone that may accompany low levels of T4 hormone (depending on the stage of critical disease) and absence of previous primary thyroid and pituitary disease.

Exclusion Criteria:

• age below 18,
• patients with a history of thyroid disease or an enlarged thyroid gland,
• psychiatric patients,
• patients on hormone therapy (excluding insulin),
• those taking amiodarone, corticosteroids or dopamine
• pregnant or postpartum mothers 6 months ago,
• patients who refuse to participate in the study