In a separate study, a 3-month course of oral iron was shown not to increase haemoglobin in a subgroup of patients with cystic fibrosis and functional iron deficiency (defined as TSat <16%).34 However, a very small case series of adult patients with cystic fibrosis given intravenous iron for anaemia refractory to oral iron found that haemoglobin concentration and MCV rose significantly within days of therapy.35 These findings are consistent with suppression of iron absorption by hepcidin. This evidence concerns the gene HAMP and cystic fibrosis.