Here is an interesting finding: low free T3 is significantly associated with increased cardiovascular and all-cause mortality in 7 prospective study on hospitalized patients.
This study doesn't find evidence of low t3-syndrome, but suggests the impairment of TSH secretion (low TSH)is the first potential sign of thyroid dysfunction.
The common feature of these disorders is a low level of circulating T3, with generally normal to slightly elevated blood T4 levels and either normal or slightly suppressed TSH levels. This pattern of altered thyroid hormone levels is generally agreed to be a result of impairment in extra-thyroidal peripheral metabolism
proportionally associated with disease severity and survival
nonthyroidal illness syndrome
Patients with persistent deterioration of hormone levels (T3, T4) during the study period had higher mortality than those who normalized the function of the thyroid axis
LT3S in patients with septic shock is part of the pathophysiology of this disease and/or an associated organ (endocrine-metabolic) failure and not just an adaptive phenomenon
substitution treatment with synthetic thyroid hormones could modify the hemodynamic symptoms of septic patients, contributing in part to the decrease in their morbidity and mortality
critical illness is associated with low TSH, reduced T3, and increased rT3 production. Inflammation is critically involved in this process. This study from JCEM shows how unreliable TSH and T4 are.
This study shows that older men are associated with low TSH, reduced response to TRH, lowered T3, and normal T4 levels. The main find in this study was the decrease in pituitary responsiveness to TRH and the reduced TSH as we age. TSH is unreliable as a test.
his study revealed that long-term low-level lead exposure may lead to reduced FT4 level without significant changes in TSH and T3 levels in adolescents even at low Pb-B levels.