Subclinical Hypothyroidism and Euthyroid Sick Syndrome in Patients with Moderate-to-Severe Congestive Heart Failure

Thyroid function tests were performed on baseline plasma that had been taken from 34 patients with NYHA Class II or Class III congestive heart failure (CHF). All patients were negative for thyroid disease on history and physical examination and none was taking medication known to alter thyroid metabolism. Analysis of thyroid function revealed abnormalities in 16 of 31 patients. These abnormalities fell into two categories: nine patients had elevated baseline thryroid stimulating hormone (TSH) above the normal limit while only one of these nine had subnormal thyroxine (T(4)) concentrations, suggesting the possibility of subclinical hypothyroidism. Seven patients demonstrated changes consistent with euthyroid sick syndrome (ESS). Weak correlations were observed between age and concentrations of T(4) and tri-iodothyronine (T(3)) and this suggests that changes in thyroid function cannot be explained solely on the basis of age. Although previous studies have demonstrated the presence of ESS in CHF, the present study suggests the possibility of a significant prevalence of subclinical hypothyroidism.