Testosterone Administration During Energy Deficit Suppresses Hepcidin and Increases Iron Availability for Erythropoiesis

Context: Severe energy deprivation markedly inhibits erythropoiesis by restricting iron availability for hemoglobin synthesis. Objective: The objective of this study was to determine whether testosterone supplementation during energy deficit increased indicators of iron turnover and attenuated the decline in erythropoiesis compared to placebo. Design: This was a 3-phase, randomized, double-blind, placebo-controlled trial. Setting: The study was conducted at the Pennington Biomedical Research Center. Patients or Other Participants: Fifty healthy young males. Intervention(s): Phase 1 was a 14-day free-living eucaloric controlled-feeding phase; phase 2 was a 28-day inpatient phase where participants were randomized to 200 mg testosterone enanthate/week or an isovolumetric placebo/week during an energy deficit of 55% of total daily energy expenditure; phase 3 was a 14-day free-living, ad libitum recovery period. Main Outcome Measure(s): Indices of erythropoiesis, iron status, and hepcidin and erythroferrone were determined. Results: Hepcidin declined by 41%, indicators of iron turnover increased, and functional iron stores were reduced with testosterone administration during energy deficit compared to placebo. Testosterone administration during energy deficit increased circulating concentrations of erythropoietin and maintained erythropoiesis, as indicated by an attenuation in the decline in hemoglobin and hematocrit with placebo. Erythroferrone did not differ between groups, suggesting that the reduction in hepcidin with testosterone occurs through an erythroferrone-independent mechanism. Conclusion: These findings indicate that testosterone suppresses hepcidin, through either direct or indirect mechanisms, to increase iron turnover and maintain erythropoiesis during severe energy deficit.