What Causes Iron Deficiency While Suffering From Crohn S Disease?

My wife was diagnosed with mild Crohns in 2014. Her inflammation seems under control and symptoms have improved, but its a day to day thing. Her issue is ongoing iron defiency which has not to date, been corrected with iron infusions. (8 infusions in 24 months). Her blood results are Haemg 86, Crits low, RBC normal, M CV down, MCH down, MCHC down. Iron studies Iron 1 L S Transferrin 3.2 normal to high Transferrin Sat 3 L Ferritin 4 L Is this Indicative of classic Iron Deficiency, or is there something else going on Her FBC results were all normal