A significant reduction of serum hepcidin concentration to 34% and 33% following 24- and 72-hours supplementation of vitamin D2 (100 000 IU) in 7 healthy participants, respectively, was observed in the Bacchetta’s study supporting the in vitro findings, and a moderate but significant negative association between changes in serum hepcidin and 25(OH)D concentrations (r = -0.38, p = 0.02) were observed in 38 kidney patients randomized to receive vitamin D3 (50 000 IU/week), and every other week for 40 weeks or placebo in Zughaier’s. The gene discussed is HAMP; the disease is medical procedure.