Effect of one time high dose "stoss therapy" of vitamin D on glucose homeostasis in high risk obese adolescents

Objective: To study the effect of using a one time high dose "stoss therapy" of vitamin D2 (ergocalciferol: VD2) on indices of insulin sensitivity {whole body sensitivity index: WBISI} and secretion {insulinogenic index: IGI} measured during an oral glucose tolerance test (OGTT) in obese adolescents with VDD (25 OHD; serum metabolite of vit D: < 30 ng/dL). Subjects and methods: In a randomized placebo controlled cross over design 20 obese adolescents with vitamin D deficiency (VDD) had baseline OGTT. Arm A received one time high dose 300,000 IU of ergocalciferol and Arm B received placebo. After 6 weeks the adolescents were reassigned to Arm A if they were in Arm B and vice versa. 25OHD, calcium, parathyroid hormone, comprehensive metabolic panel, urine calcium creatinine ratio were measured at each study visit. OGTTs to assess indices of sensitivity and secretion were done at baseline, 6 weeks and 12 weeks respectively. Results: Adolescents were obese and insulin resistant (mean +/- SD: mean age = 15.1 +/- 1.9 years; BMI: 32.7 +/- 9.8; homeostatic model of insulin resistance: HOMA-IR: 4.2 +/- 2.8). Stoss therapy with VD2 increased 25OHD from baseline (16.7 +/- 2.9 to 19.5 +/- 4.5; p = 0.0029) when compared to the placebo. WBISI (2.8 +/- 1.9) showed a trend towards improvement in Rx group (p = 0.0577) after adjustment for covariates. IGI (3 +/- 2.2) showed an improvement in both Rx and placebo groups. Conclusions: Our study demonstrated that using a high dose of VD2 (300,000 IU) did not have any beneficial effect on insulin sensitivity (whole body sensitivity index {WBISI}) and secretory indices (insulinogenic index {IGI}) in obese adolescents. High dose "stoss therapy" of VD2 did not appear to have any beneficial effect on glucose homeostasis on obese adolescents.