Plasma intact fibroblast growth factor 23 levels in women with bulimia nervosa: A cross-sectional pilot study

Fibroblast growth factor (FGF) 23, a circulating 26-kDa peptide produced by osteogenic cells, is a novel phosphaturic factor, which is important for the regulation of inorganic phosphate homeostasis and for vitamin D metabolism [1]. FGF23 inhibits renal proximal tubule phosphate reabsorption, increases renal phosphate excretion, and reduces serum phosphate without affecting serum calcium. FGF23 also strongly suppresses 1,25-dihydroxyvitamin D (1,25-(OH)2D) production [2,3].Circulating FGF23 levels are regulated by serum phosphate [4,5], 1,25-(OH)2D [3,6] and dietary phosphate [6]. Dietary phosphate plays an important role in FGF23 regulation, and dietary phosphate loading increases circulating FGF23 levels in healthy men in a matter of days [7], even without changes in serum phosphate or 1,25-(OH)2D levels [8].Bulimia nervosa (BN) is an eating disorder characterized by habitual binge eating, inappropriate compensatory behaviors, such as self-induced vomiting, a preoccupation with body weight, and excessive self-evaluation of weight and shape. For BN, the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) specifies that binging and compensatory behaviors must occur with a minimum average frequency and duration of at least twice a week for three months [9].Our previous study showed that binge-eating/purging type anorexia nervosa (AN-BP) patients had elevated plasma intact FGF23 (iFGF23) levels, while restricting type (AN-R) patients had plasma iFGF23 levels similar to healthy controls [10]. Although BN patients as well as some patients with AN-BP regularly engage in binge eating, there have been no previous studies regarding plasma iFGF23 levels in BN patients. Therefore, the present study was performed to determine plasma iFGF23 concentrations in BN patients and healthy controls.The study population consisted of 13 female outpatients of The University of Tokyo Hospital diagnosed with purging type BN according to DSM-IV by experienced clinic