Vitamin D Status and Its Relation to Age and Body Mass Index

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Abstract
Background/Aims: While numerous studies have examined 25(OH)-vitamin D3 (25-D) concentrations and their relation to parathyroid hormone (PTH) levels there is only limited information on the interrelation between 25-D, 1,25(OH)2-vitamin D3 (1,25-D) and PTH. It was the aim of this study to assess the vitamin D endocrine system and its relation to age and body mass index (BMI). Methods: This cross-sectional study comprised a convenience sample of 483 adults which attended the endocrinology outpatient service of a university hospital in the years 2002–2004. Results: The mean concentrations of 25-D, 1,25-D, calcium and PTH were 21.0 ± 10.6 ng/ml, 47.9 ± 21.7 pg/ml, 9.48 ± 0.48 mg/dl and 51.0 ± 27.2 pg/ml, respectively. 25-D was related (p < 0.01) to BMI, age, PTH and 1,25-D. After correction for 25-D, we found no relation between BMI and 1,25-D. PTH was related (p < 0.01) to serum calcium, BMI, age and 1,25-D (p = 0015). There was a seasonal variation in both, 25-D and 1,25-D serum concentrations: 25-D levels were lowest in January and increased until July while the nadir and zenith of 1,25-D were found in April and October, respectively. Conclusion: Since BMI was negatively related to 25-D the prevalence of 25-D deficiency (30 kg/m2. BMI, age and season should be taken into account when assessing a patients vitamin D status and more aggressive vitamin D supplementation should be considered for obese subjects.