NEPHROLOGY - ORIGINAL PAPER Comparison of the prevalence of calcidiol insufficiency in predialysis and osteoporotic populations Jose ´e Bouchard Æ Denis Ouimet Æ Michel Valle ´e Æ Jean-Philippe Lafrance Æ Martine Leblanc Æ Lyne Se ´ne ´cal Æ Alain Bonnardeaux Æ Jean-Pierre Mathieu Æ Vincent Pichette Received: 29 August 2008 / Accepted: 11 November 2008 / Published online: 5 December 2008 Ó Springer Science+Business Media, B.V. 2008 Abstract Aim Calcidiol insufficiency is highly prevalent in chronic kidney disease (CKD) and osteoporotic patients. We assessed and compared calcidiol levels in these two groups from the same geographical area to differentiate environmental factors from charac- teristics related to CKD. Methods We measured calcidiol levels in 160 predialysis (group 1) and 53 osteoporotic (group 2) patients from a single center. Calcidiol insufficiency was defined as a level between 37.5 and 75 nmol/l and calcidiol deficiency was defined as a level below 37.5 nmol/l. Results In group 1, mean glomerular filtration rate (GFR), calcidiol, and parathyroid hormone (PTH) levels were 18.3 ± 4.7 ml/min, 38.7 ± 15.1 nmol/l, and 21.9 ± 19.1 pmol/l. Calcidiol insufficiency and deficiency were present in 98.7% of patients. There was an inverse correlation between calcidiol and PTH levels (r =-0.25; P = 0.001). In group 2, mean GFR, calcidiol levels, and PTH levels were 68.6 ± 17.6 ml/min, 73.8 ± 27.1 nmol/l, and 4.23 ± 1.83 pmol/l, respectively. Calcidiol insufficiency and deficiency were present in 50.9% of patients. There was an inverse correlation between calcidiol and PTH levels (r =-0.44; P = 0.02). Conclusion In our predialysis population, calcidiol insufficiency and deficiency are present in almost every patient, being more common than previously reported. It is also more frequent than in a similar osteoporotic population, suggesting a cause unrelated to environmental factors. Interestingly, there is a significant inverse correlation between calcidiol and parathyroid levels in both populations. Further stud- ies are needed to enable understanding of the mechanisms underlying calcidiol insufficiency. Keywords Calcidiol Á Chronic kidney disease Á Hyperparathyroidism Á Osteoporosis Á Parathyroid hormone Introduction There has been increasing interest in calcidiol in chronic kidney disease (CKD) populations because studies have linked calcidiol deficiency to hyperpara- thyroidism (HPT) [1–3]. Calcidiol (25(OH)D) deficiency is defined as a level less than 37.5 nmol/ l, and insufficiency as a level between 37.5 and J. Bouchard Á D. Ouimet Á M. Valle ´e Á J.-P. Lafrance Á M. Leblanc Á L. Se ´ne ´cal Á A. Bonnardeaux Á V. Pichette (&) Service de ne ´phrologie, Ho ˆpital Maisonneuve-Rosemont, Universite ´ de Montre ´al, 5415 Blvd. de l 0 Assomption, Montreal, QC, Canada H1T 2M4 e-mail: vpichette.hmr@ssss.gouv.qc.ca J.-P. Mathieu Service de rhumatologie, Ho ˆpital Maisonneuve- Rosemont, Universite ´ de Montre ´al, Montreal, Canada 123 Int Urol Nephrol (2009) 41:983–988 DOI 10.1007/s11255-008-9509-6