title: Relationship between Biochemical Bone Markers and Bone Mineral Density in Patients with Phenylketonuria under Restricted Diet.
abstract: OBJECTIVE
  Most of phenylketonuria (PKU) develops bone turnover impairment and low bone mineral density (BMD). Measurements of BMD reﬂect only bone mineral status but not the dynamics of bone turnover. Bone markers are a noninvasive tool useful for the assessment of bone formation and bone resorption processes. Our study was to assess the levels of bone markers in PKU in order to select a screen marker and detect the most specific marker which can be combined with BMD for appropriate follow up.
  
  
  METHODS
  Thirty three classic PKU patients were studied. BMD and bone mineral content (BMC) were measured. Total alkaline phosphatase (ALP), osteocalcin (OC) and carboxy-terminal propeptide of type I collagen (CICP), osteoprotegerin (OPG), receptor activator of nuclear factor κβ ligand (RANKL) and Deoxypyridinoline (DPD) were measured. Findings : Nineteen (57.6%) male and fourteen (42.4 %) female PKU patients were involved in the current study. Their mean age was 8.4±4.6 yrs and the age range 3-19 yrs. The control group consisted of twenty two (52.4%) males and twenty (47.6%) females. Their mean age was 8.5±3.3 yrs and th age range 2-17 yrs. Using the Z score values, there was a significant decrease of total BMC (TBMC-Z), BMD of the femoral neck BMD-FN-Z, BMD of lumbar vertebrae (BMD-L-Z), BMD-FN and DPD while RANKL increased. There was a negative correlation between CICP and TBMC and between CICP and BMD-L in these patients. Also, a negative correlation between ALP and TBMC and between ALP and BMD-L was observed. It was concluded that the ALP provides a good impression of the new bone formation in the PKU patients and it has a highly significant negative correlation with the many parameters of the bone mineral status beside the wide availability of inexpensive and simple methods. So a screening test and/or follow up for the PKU patients using ALP would be available. Once the level of ALP decrease is detected, one can combine it with BMD to explore the bone mineral status and with specific bone markers (OC, RANKL and DBD), to verify the dynamics of bone turnover.
  
  
  CONCLUSIONS
  This schedule will reduce the risk of exposure of these patients to the risk hazards of DXA and limit its use only to a limited number of the highly suspected cases.
authors: Department of Pediatrics, National Research Centre.
authors: Hala M
authors: HM
authors: Koura
authors: Department of Anatomy, Faculty of Medicine.
authors: Sherif M
authors: SM
authors: Zaki
authors: Department of Pediatrics, National Research Centre.
authors: Nagwa A
authors: NA
authors: Ismail
authors: Department of Pediatrics, National Research Centre.
authors: Emad E
authors: EE
authors: Salama
authors: Clinical Pathology Department, National Research Centre.
authors: Dalia H
authors: DH
authors: El Lebedy
authors: Department of Molecular Genetics, National Research Centre, Cairo University, Cairo, Egypt.
authors: Laila K
authors: LK
authors: Effat
keywords: Bone Mineral Content; Bone Mineral Density; Osteocalcin; PKU; Phenylketonuria; RANKL