Predictors and relationships of serum 25 hydroxyvitamin D concentration with bone turnover markers, bone mineral density, and vitamin D receptor genotype in Emirati women Hussein F. Saadi a, ⁎ , Nicolaas Nagelkerke b , Sheela Benedict a , Hussein S. Qazaq c , Erica Zilahi d , Mohammad K. Mohamadiyeh e , Abdulrahim I. Al-Suhaili e a Department of Internal Medicine, Faculty of Medicine and Health Sciences, United Arab Emirates University, P O Box 17666, Al Ain, UAE b Department of Community Medicine, Faculty of Medicine and Health Sciences, United Arab Emirates University, UAE c Department of Nutrition, Ministry of Health, Tawam Hospital, General Authority for Health Services for Abu Dhabi, Al Ain, UAE d Department of Medical Microbiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, UAE e Division of Nuclear Medicine, Tawam Hospital, General Authority for Health Services for Abu Dhabi, Al Ain, UAE Received 23 November 2005; revised 7 May 2006; accepted 11 May 2006 Available online 30 June 2006 Abstract Objectives: To determine factors influencing serum 25 hydroxyvitamin D (25OHD) concentration and relationships between serum 25OHD concentration, bone turnover markers, bone mineral density (BMD), and vitamin D receptor (VDR) genotype in Emirati women. Methods: Serum 25OHD, parathyroid hormone (PTH), osteocalcin (OC), vitamin D binding protein (VDBP), and urinary deoxypyrdinoline (UDPD) concentrations and VDR genotype were determined in Emirati women volunteers who were participating in a study aiming at establishing a reference database for BMD. Results: Serum 25OHD concentration in the 259 women volunteers was 25.3 ± 10.8 nmol/l (mean ± SD), and all had vitamin D deficiency (25OHD <80 nmol/l). Mean serum 25OHD was highest in April (29.2 ± 13.0 nmol/l), which marks the end of the short and cooler winter season, and lowest in August (18.2 ± 5.9 nmol/l). No significant difference in 25OHD concentration was noted among Emirati women wearing different dress styles, but the mean serum 25OHD was significantly lower in comparison with non-Arab Caucasian women volunteers who dressed in a Western style (P < 0.001). Serum 25OHD correlated positively with age (r = 0.2), number of pregnancies (r = 0.16), dietary vitamin D intake (r = 0.15), serum calcium (r = 0.14), phosphorus (r = 0.14), VDBP (r = 0.15), and urinary calcium/creatinine (r = 0.2), and inversely with PTH (r = -0.22), OC (r = -0.13), and UDPD/creatinine (r = -0.15); P < 0.05 for all correlations. Multiple linear regression analysis showed that age, dietary vitamin D intake, multivitamin intake, and cooler season were independent positive predictors of serum 25OHD concentration (R 2 = 0.18). The frequencies of VDR genotypes were 36% GG, 44.1% AG, and 19.9% AA. Allele frequencies were 58% for G allele and 42% for A allele and were in Hardy– Weinberg equilibrium (x 2 = 1.44; P > 0.1). There was no statistically significant influence of VDR genotype on bone turnover or BMD. Conclusions: Vitamin D deficiency is highly prevalent in Emirati women and appears largely attributable to insufficient sunlight exposure. It is associated with increased bone turnover. VDR genotype does not appear to influence bone turnover markers or BMD in Emirati women. © 2006 Elsevier Inc. All rights reserved. Keywords: 25 hydroxyvitamin D; Emirati women; Bone turnover markers; Bone mineral density; Vitamin D receptor genotype Introduction Vitamin D deficiency results from inadequate synthesis in the skin, decreased dietary intake, impaired vitamin D ac- tivation in the liver and kidney, or resistance to vitamin D action [1–6]. Vitamin D nutritional status is best assessed by measurement of the serum 25 hydroxyvitamin D (25OHD) concentration [4–6]. Serum concentrations <20 nmol/l indicate moderate to severe vitamin D deficiency that leads to rickets or histologically evident osteomalacia [5–7]. Mild vitamin D deficiency (25OHD <80 nmol/l) may be associated with Bone 39 (2006) 1136 – 1143 www.elsevier.com/locate/bone ⁎ Corresponding author. Fax: +97137672995. E-mail address: saadih@uaeu.ac.ae (H.F. Saadi). 8756-3282/$ - see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.bone.2006.05.010