Is There Any Kind Of Gastrointestinal Disorders That Can Cause

Is there any kind of gastrointestinal disorders that can cause a severe iron deffiency? There is no blood in the stool, (coffee ground, fresh, etc) My mom was a GI tech for around 20 years before she passed, I remember her talking once about a disorder with the bowels, (small intestine) if I remember correctly, that can cause this, but it was not common, and not easily diagnosed. Thank you in advance for any info you can offer.