Early manifestations of "sick euthyroid" syndrome in patients with compensated chronic heart failure

Background: A "sick euthyroid" syndrome occurs in patients with severe decompensated chronic heart failure (CHF) and other chronic illnesses and is related to adverse prognosis, but it has not been described in patients with compensated CHF. The aim of this study was to determine whether manifestations of the sick euthyroid syndrome occur in patients with compensated CHF caused by ischemic heart disease. Methods and Results: Thyroid hormonal responses to thyrotropin-releasing hormone (TRH) stimulation were compared in 8 patients with New York Heart Association class I/II CHF considered secondary to ischemic heart disease and 7 control patients after serial 10-minute blood sampling over 3-hour periods. Secretory dynamics of TRH-induced thyroid-stimulating hormone (TSH) release were compared by using deconvolution analysis. Changes in serum thyroxine (T₄), triiodothyronine (T₃), reverse T3 (rT₃), and rT₃/T₄ concentration ratios were compared. Patients with CHF had lower baseline serum T₃ concentrations (P <.001), with lower maximum serum T₃ (P <.01) and higher maximum serum rT₃ (P <.05) concentrations after TRH stimulation but similar estimated TRH-induced TSH secretory burst amplitude, mass, and 3-hour production rates, compared with control patients. Conclusions: Patients with compensated CHF display the derangements in thyroid hormone metabolism of impaired peripheral conversion of T₄ and T₃ and increased production of rT₃ in the presence of normal dynamic function of the hypothalamic-pituitary-thyroid axis, which are consistent with early manifestations of a sick euthyroid state.