Involvement of circulating interleukin-6 and its receptor in the development of euthyroid side syndrome in patients with acute myocardial infarction

Objective: In patients with acute myocardial infarction (AMI), low triiodot hyronine (T-3) levels with normal or subnormal levels of thyrotropin (TSH), the euthyroid sick syndrome (ESS), have been reported, however. the mechan ism of altered thyroid hormone metabolism is unknown. Recent reports have s hown that interleukin-6 (IL-6) plays a key role in the pathogenesis of AMI and ESS. This preliminary study investigates the relationship between thyro id states and plasma levels of IL-6, the soluble IL-G receptor (sIL-6R), an d the soluble transducing 130 KDa glycoprotein (sgp 130) in AMI. Design and methods: We measured the concentration of TSH, free T-3 (FT3), f ree thyroxine (FT4), IL-6, sIL-6R and sgp130 in plasma from 24 patients vii th AMI and 20 normal controls. Results: All 24 AMI patients showed significantly lower concentrations of F T3 with normal or subnormal levels of TSH, and higher concentrations of IL- 6 and sIL-6R than controls. IL-6 level was correlated with creatine phospho kinase (CPK) and FT3 levels but not with FT4 or TSH levels in patients with AMI. The time course of IL-6 and FT3 concentration seemed to be closely li nked. sIL-6R level was correlated with CPK and sgp130 levels, but not with FT3, FT4 or TSH levels. FT4 level was correlated with sgpl30 level. Conclusion: Patients with AMI develop ESS through activation of IL-6 and it s receptor system.