Hypothyroidism and renal function in patients with systolic heart failure

The extent to which hypothyroidism affects renal function in patients with heart failure remains incompletely explored, despite the known adverse prognostic implications of renal dysfunction in these patients. In a pilot retrospective study, we evaluated 75 patients (age, ≥18 yr) with left ventricular ejection fractions <0.40. Forty-five patients had normal thyroid function (thyroid-stimulating hormone [TSH], 0.35-5.5 μIU/mL) and 30 had hypothyroidism. The group with hypothyroidism was subdivided into 17 patients who had controlled hypothyroidism (TSH, 0.35-5.5 μIU/mL) and 13 who had uncontrolled hypothyroidism (TSH, >5.5 μIU/mL). Renal function, measured in terms of glomerular filtration rate, was analyzed once in each patient, and the populations were statistically compared, with P <0.05 conferring statistical significance. Baseline characteristics in all groups were similar. Mean glomerular filtration rate was better in patients with normal thyroid function than those with hypothyroidism (75.45 ± 31.48 vs 63.95 ± 21.43 mL/min/1.73 m²; P=0.032). There was no significant difference between patients with controlled hypothyroidism (66.89 ± 24.18 mL/min/1.73 m²) and those with normal thyroid function (P=0.131). In patients with uncontrolled hypothyroidism, mean glomerular filtration rate (60.2 ± 17.4 mL/min/1.73 m²) was significantly worse than in patients with normal thyroid function (P=0.015). We found that heart-failure patients with insufficiently treated hypothyroidism have worse renal function than do patients whose thyroid function is normal or whose hypothyroidism is effectively treated. Larger studies will be needed in order to evaluate this conclusion further. We recommend that hypothyroidism in heart-failure patients be strictly controlled, lest it affect prognosis adversely.