Answer: Your daughter has iron deficiency anemia either because she's losing blood somewhere or her body's not properly absorbing iron from her diet.
Causes of blood loss in a premenopausal woman include bleeding from the digestive tract and heavy menstrual bleeding. Endoscopy has ruled out the obvious sources: esophagus, stomach, duodenum and colon. Some women think their menstrual bleeding is normal when it is not, so it would be worth having her doctor rule out a gynecological source like a uterine fibroid or polyp.
If bleeding has been ruled out and she feels well, her anemia has been slow and chronic. The most common cause for iron deficiency anemia in that case is malabsorption in the small intestine from celiac sprue - a condition in which the immune system reacts abnormally to gluten protein.
It's a mysterious autoimmune reaction; for unclear reasons, gluten protein triggers a destruction of the tiny villi projections in the small intestine that are responsible for the absorption of not only iron, but all sorts of important nutrients.
While most commonly seen in childhood, it can first appear in adulthood. Depending upon the degree of small-bowel destruction, there may or may not be weight loss and diarrhea with celiac sprue.
Diagnosis involves blood tests that look for celiac antibodies and a small-bowel study with biopsy. Correction of the condition requires daily iron and a gluten-free diet.
If it turns out that she does not have celiac and no clear cause for iron deficiency is found, I'd suggest seeing a hematologist for further evaluation and IV iron infusion.
Mitchell Hecht is a physician specializing in internal medicine. Send questions to: Ask Dr. H, Box 767787, Atlanta, Ga. 30076. Because of the volume of mail, personal replies are not possible.