Iron deficiency after Roux-en-Y Gastric Bypass: insufficient iron absorption from oral iron supplements Ina GESQUIERE, PharmD; Matthias LANNOO, M.D.; Patrick AUGUSTIJNS, PhD PharmD; Christophe MATTHYS, PhD; Bart VAN DER SCHUEREN, PhD M.D.; Veerle FOULON, PhD PharmD Manuscript type: Original contribution Correspond to: Ina Gesquiere Ina Gesquiere e-mail: [email protected] Department of Pharmaceutical and Pharmacological Sciences, KU Leuven O&N2, Herestraat 49, box 521 3000 Leuven Belgium Tel: + 32 16 32 34 47 Fax: + 32 16 32 34 68 Authors: Matthias Lannoo e-mail: [email protected] Department of Abdominal Surgery UZ Leuven Campus Gasthuisberg Herestraat 49 3000 Leuven Belgium 1

Patrick Augustijns e-mail: [email protected] Department of Pharmaceutical and Pharmacological Sciences O&N2, Herestraat 49 box 921 3000 Leuven

Christophe Matthys e-mail: [email protected] Laboratory of Clinical and Experimental Endocrinology UZ Leuven Campus Gasthuisberg Herestraat 49, box 7003 3000 Leuven

Bart Van der Schueren e-mail: [email protected] Laboratory of Clinical and Experimental Endocrinology UZ Leuven Campus Gasthuisberg Herestraat 49, box 902 3000 Leuven

Veerle Foulon e-mail: [email protected] Department of Pharmaceutical and Pharmacological Sciences O&N2, Herestraat 49, box 521

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3000 Leuven Belgium

Running head: Iron absorption after RYGB

Acknowledgements Ina Gesquiere receives a PhD scholarship from the Agency for Innovation by Science and Technology, Flanders, IWT-111328. The authors declare no conflict of interest.

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Abstract Background Roux-en-Y gastric bypass (RYGB) may reduce the absorption of iron, but the extent to which this absorption is impeded is largely unknown. First, we determined the prevalence of iron deficiency following RYGB and explored the risk factors for its development. Second, we examined to what extent oral iron supplements are absorbed after RYGB. Methods Monocentric retrospective study in 164 patients (123 female, 41 male; mean age 43 years) who underwent RYGB between January 2006 and November 2010. Pre-and postoperative data on gender, age, BMI, serum levels of iron, ferritin, hemoglobin, vitamin B12, 25-hydroxy vitamin D, and use of proton pump inhibitors and H2-antagonists were collected. Generalized linear mixed models were used for the analysis of the data. In 23 patients who developed iron deficiency after surgery, an oral challenge test with 100 mg FeSO4.7H2O was performed. Results Following RYGB, 52 (42.3%) female patients and 9 male (22.0%) patients developed iron deficiency (serum ferritin concentration ≤ 20 µg/L). The prevalence of iron deficiency was significantly higher in females than males (p=0.0170). Young age (p=0.0120), poor preoperative iron status (p=0.0004), vitamin B12 deficiency (p=0.0009) and increasing time after surgery (p