Plasma interleukin-2 levels and thyroid function in elderly patients with nonthyroidal illness

To determine whether interleukin-2 (IL-2) plasma concentrations are modified in patients with nonthyroidal illness (NTI) and thyroid function alterations, we measured plasma concentrations of T 3, T 4, free T 3 (FT 3), free T 4 (FT 4), TSH, and IL-2 in 34 elderly NTI patients and in 25 age- and sex-matched healthy controls. IL-2 was detectable in 11 of the 34 patients. Patients with detectable IL-2 plasma levels had significantly lower plasma T 3 and FT 3 concentrations when compared to those with undetectable IL-2. Moreover, IL-2 plasma levels were positively correlated to reverse T 3 (rT 3), ( r S=0.67, P