[The beneficial effects of iron supplementation other than improvement of anemia].
Previous randomized controlled trials (RCTs) have shown beneficial effects of iron supplementation other than anemia improvement including treatment of restless leg syndrome and general fatigue, even in non-anemic subjects with iron deficiency. Recently, some RCTs in congestive heart failure (CHF) demonstrated that intravenous administration of ferric carboxymaltose improves patient symptoms and reduces incidence of hospitalization for worsening heart failure. Consequently, the European Society of Cardiology recommends that iron deficient patients with CHF are administered ferric carboxymaltose (evidence level A). Moreover, the PIVOTAL study for hemodialysis patients proved that proactive administration of iron sucrose decreases the dose of erythropoiesis-stimulating agents and frequency of transfusion compared with its sole administration in reaction to iron deficiency. Notably, this proactive treatment is superior to a low-dose regimen in preventing the primary composite endpoints of nonfatal myocardial infarction, stroke, hospitalization for CHF, and death. These clinical findings are supported by basic research on cardiomyocyte-specific transferrin receptor knock-out mice showing heart failure with impaired mitochondrial respiratory function. In this model, cardiac iron deficiency impairs the mitochondrial electron transport chain, thus leading to low adenosine triphosphate production, and it subsequently prevents mitophagy resulting in damaged mitochondrial accumulation in the heart.