Free and Bioavailable Vitamin D Levels of Patients with Type 1 Diabetes Mellitus and Association with Bone Metabolism

Ceyda Dincer Yazan; Ali Yaman; Goncagul Haklar; Onder Sirikci; Oguzhan Deyneli

doi:10.1007/s40200-022-01032-0

Free and Bioavailable Vitamin D Levels of Patients with Type 1 Diabetes Mellitus and Association with Bone Metabolism

J Diabetes Metab Disord. 2022 Apr 5;21(1):689-695. doi: 10.1007/s40200-022-01032-0. eCollection 2022 Jun.

Authors

Ceyda Dincer Yazan¹, Ali Yaman², Goncagul Haklar², Onder Sirikci², Oguzhan Deyneli³

Affiliations

¹ Department of Endocrinology and Metabolism, Marmara University School of Medicine, Istanbul, Turkey.
² Department of Biochemistry, Marmara University School of Medicine, Istanbul, Turkey.
³ Department of Endocrinology and Metabolism, Koc University School of Medicine, Istanbul, Turkey.

Abstract

Aim: Vitamin D deficiency is known to be associated with metabolic bone diseases. The aim of this study is to evaluate vitamin D and calculated free and bioactive vitamin D levels of type 1 diabetic patients and to evaluate the association with bone turnover markers.

Method: This cross-sectional study includes 60 patients admitted to endocrinology outpatient clinic with diagnosis of type 1 diabetes mellitus and 60 controls. Weight, height and waist circumference were recorded and blood samples were taken for measurement of 25-hydroxyvitamin D (25(OH)D), vitamin D binding protein (VDBP), osteocalcin, bone alkaline phosphatase (bone-ALP), c-telopeptide. Free and bioavailable vitamin D levels were calculated with formula.

Results: Vitamin D levels of type 1 diabetic patients were significantly higher (p = 0.01). Parathormone levels of the group with vitamin D level under 20 ng/ml was significantly higher (p = 0.029). VDBP levels were similar in both groups. Correlation analysis of free and bioavailable vitamin D level with osteocalcin, c-telopeptide, bone alkaline phosphatase revealed only a weak significant correlation between free vitamin D and osteocalcin (r = -0.201; p = 0.028). A negative correlation was determined between 25(OH)D and parathormone levels (r = -0.294; p < 0.005). Serum osteocalcin, bone alkaline phosphatase and c-telopeptide levels of control group were significantly higher.

Conclusion: 25(OH)D levels of the study population was extremely low. The measurement of VDBP and calculated free and bioactive vitamin D levels did not show a better correlation with bone turnover markers according to 25(OH)D levels.

Keywords: Bioavailable vitamin D; Free vitamin D; Type 1 DM; VDBP.