HAMP and Crohn disease: In one study, six pediatric patients with active Crohn's disease (defined as an IL-6 level >5 pg/mL) had poor absorption of a single dose of oral iron and high urinary hepcidin levels (mean 295.3 ng/mg creatinine) compared to ten patients with relatively inactive Crohn's disease (with IL-6 levels ≤5 pg/mL and mean urinary hepcidin levels 31.22 ng/mg creatinine).