Relationship between triiodothyronine and proinflammatory cytokines in chronic heart failure

Cytokines and thyroid hormones are involved in the biochemical changes associated to heart failure (HF).

Aims of the study were to investigate: plasma circulating levels of the cytokines Interleukine-6 (IL-6) TNF alpha and C reactive protein (CRP) in patients with stable HF in relation to the severity of left ventricular dysfunction; the relationship between these inflammatory markers and thyroid hormones.

One-hundred and sixty-six patients (121 males, age 64+/-12), with non-ischemic cardiomyopathy, were admitted to the Institute of Clinical Physiology for progressive deterioration of symptoms. Forty-eight healthy subjects (30 males, age range 26-75 years) were also enrolled as control group (Group N). High sensitivity (hs)-IL-6 and hs-TNFalpha were quantified using solid phase sandwich ELISA kits. Hs-CRP was measured by Immulite System.

In the whole population (HF and N), the association between inflammatory markers and age resulted statistically significant only for IL-6 serum concentration (p<0.001) but not for TNFalpha and CRP. IL-6 and TNFalpha were strongly higher in the HF in comparison with N (p<0.001) while CRP showed a less significant difference (p<0.05). Whole population showed a negative association between IL-6 and EF% and between CRP and EF% (respectively p<0.01, r=-0.23; p<0.05, r=0.19). Comparing normal subjects with two classes of patients, respectively with EF>35% and EF<35%, we clearly observed the progressive enhancement of the inflammatory markers. Considering normal subjects, patients without and with low T3 syndrome, IL-6 and TNFalpha increased progressively from normal to patients with fT3<2 pg/ml (p<0.01 and p<0.01) while CRP only respect to the group with low T3 syndrome (p<0.01). The inflammatory markers were all inversely correlated with FT3 levels.

Because low FT3 serum concentration represents a negative prognostic index, it is likely that impairment of T3 production and enhanced inflammation represent pathogenic mechanisms linked to HF progression.