Post-thyroidectomy thyroxine replacement dose in patients with or without compensated heart failure: The role of cytokines

Objective: To investigate the potential association between serum inflammatory cytokine levels and post-thyroidectomy thyroxine replacement dose in patients with or without compensated heart failure. Patients and methods: The study included 42 patients (group A: 20 men, mean age of 54.5 ± 6.8 years) with NYHA I or II heart failure and 54 patients (group B: 25 men, mean age of 52.9 ± 7.1 years) without heart failure. All patients had undergone total thyroidectomy and were euthyroid on a stable thyroxine replacement dose. Serum Interleukin-1b (IL-1b), Tumor Necrosis Factor α (TNF-α), Interleukin-6 (IL-6), TSH, T3, T4, fT3 and fT4 were measured. Results: Both groups exhibited a significant positive correlation between IL-6 and levothyroxine replacement dosage (group A: r = 0.708, p < 0.001; group B: r = 0.345, p = 0.012) and a negative correlation between IL-6 and T3 (group A: r = −0.342, p = 0.023, group B: r = −0.294, p = 0.035). Significant independent predictors of levothyroxine replacement dosage were IL-6 (p < 0.001) and TNF-α (p = 0.007) in group A (58.3% of dosage variation) and only IL-6 (p = 0.012) in group B (10.1% of dosage variation). Conclusions: In both groups, a significant positive correlation was observed between IL-6 and levothyroxine replacement dosage, but this correlation was stronger in group A. In the same group, there was evidence for a more pronounced influence of cytokines on levothyroxine dosage.