Pediatr Nephrol (2006) 21:74–78 DOI 10.1007/s00467-005-2035-1 ORIGINAL ARTICLE Maria-Goretti Moreira Guimar¼es Penido · Eleonora Moreira Lima · Marcelo Ferraz Oliveira Souto · Viviane Santuari Parizotto Marino · Ana-Luiza Fialho Tupinambµ · Anderson França Hypocitraturia: a risk factor for reduced bone mineral density in idiopathic hypercalciuria? Received: 10 April 2005 / Revised: 13 June 2005 / Accepted: 15 June 2005 / Published online: 27 October 2005  IPNA 2005 Abstract The association between idiopathic hypercal- ciuria (IH) and reduced bone mineral density (BMD) has been described in adults and children. Frequently, hypocitraturia (HC) is an associated condition. To deter- mine the effect that HC may have on bone metabolism of these patients, we studied 88 children with IH at diag- nosis, divided into the following groups: group 1–44 (50%) patients with associated HC; group 2–44 (50%) patients without HC; group 3 (29 subjects), a healthy control group. Urinary and blood electrolytes, as long as urinary N-telopeptide, were measured. Lumbar spine (L2–L4) and femoral neck bone mineral density (BMD) and bone mineral content (BMC) were measured by dual energy X-ray absorptiometry. There was no difference in age between the three groups (P=0.80), but weight, height, body mass index, and bone age were lower (P<0.01) and serum intact parathyroid hormone (iPTH) was higher (P<0.05) in group 1 than in groups 2 and 3. N- telopeptide, measured in urine, did not differ between groups. The following bone densitometry parameters: lumbar spine BMC, BMC adjusted for height (BMCh), BMC adjusted for width of vertebrae (BMCw) and BMD, as well as femoral neck BMD, were significantly lower in group 1 than in groups 2 and 3 (P<0.01). When we cor- rected densitometry parameters for height, BMC was lower in group 1 and not in group 2 when compared with controls. Conclusions: Children with IH and associated HC may have a higher risk of bone mass loss and con- sequent osteopenia. Further studies are needed to assess the role that hypocitraturia may have in this form of bone disease. Keywords Idiopathic hypercalciuria · Idiopathic hypocitraturia · Osteopenia · Bone densitometry · N-telopeptide · BMC · BMD Introduction Idiopathic hypercalciuria (IH) is a common metabolic disorder that affects 3–9% of children (3.2% in a Brazilian population) [1, 2, 3]. It is one of the most common causes of asymptomatic hematuria, and is a significant risk factor for nephrolithiasis in childhood [4, 5]. The etiology is not known, but environmental and genetic factors may be implied [6]. The association of IH with reduction of bone mineral density (BMD) has been described in adults [7] and children [8, 9, 10]. Another important risk factor for renal calculi is id- iopathic hypocitraturia (HC). Citrate is an important in- hibitor of urinary crystallization [11], particularly oxalate [12] and calcium phosphate [13] crystals. The prevalence of hypocitraturia among patients with nephrolithiasis ranges from 26–63%, most of the time associated with other metabolic disorders [14, 15]. The aim of this study was to evaluate whether, in pa- tients studied at diagnosis, the presence of HC worsens the alterations in bone metabolism found in children and adolescents with IH. Subjects and methods Subjects Eighty-eight children and adolescents with IH, seen between July 1998 and March 2000, were divided into two groups: group 1 (25 male, 19 female), which had children with associated HC aged 1.8 years to 14.9 years (median 8.8 years) and group 2 (25 male, 19 M.-G. M. G. Penido ( ) ) Apt. 101, Rua Tome De Souza 1292, B. Lourdes, 30140-131 Belo Horizonte MG, Brazil e-mail: mariagorettipenido@yahoo.com.br Tel.: +55-31-32414466 Fax: +55-31-32414466 M.-G. M. G. Penido · E. M. Lima · M. F. O. Souto · V. S. P. Marino · A.-L. F. Tupinambµ · A. França Pediatric Nephrology Unit (GRIM), University Hospital, Federal University of Minas Gerais, Belo Horizonte, Brazil