The Relationship between 25-hydroxyvitamin D Levels, Insulin Sensitivity and Insulin Secretion in Women 3 Years after Delivery

Objectives: There is a direct correlation between 25-hydroxyvitamin D (25[OH] D) levels and insulin sensitivity. Furthermore, women with gestational diabetes (GDM) may have lower levels of 25(OH) D compared to controls. The present study intended to investigate 25(OH) D levels and their association with insulin sensitivity and insulin secretion in women with prior GDM and in controls 3.2 years after delivery. Methods: A total of 87 patients with prior GDM and 45 randomly selected controls (age range, 22 to 44 years) with normal glucose tolerance during pregnancy nested within a cohort of all deliveries at Saint Margit Hospital, Budapest, between January 1 2005, and December 31 2006, were examined. Their 25(OH) D levels were measured by radioimmunoassay. Insulin sensitivity and fasting insulin secretion were estimated using the homeostasis model asssessment (HOMA) calculator and early insulin secretion by the insulinogenic index based on a 75 g oral glucose tolerance test. Results: There was no significant difference in 25(OH) D levels between cases and controls (27.2 +/- 13.1[+/- SD] vs. 26.9 +/- 9.8 ng/L). There was a positive association between HOMA insulin sensitivity and 25(OH) D levels (beta = 0.017; 95% CI 0.001 to 0.034/1 ng/mL) that was robust to adjustment for age and body mass index. There was a nonsignificant association between HOMA insulin secretion and 25(OH) D (p=0.099), while no association was found with the insulinogenic index. Conclusions: Prior GDM status was not associated with 25(OH) D levels; however, 25(OH) D levels were associated with HOMA insulin sensitivity. It is hypothesized that the association between HOMA insulin secretion and 25(OH) D levels is related to the autoregulation of fasting glucose levels because no association between 25(OH) D and insulinogenic index was found. (C) 2017 Canadian Diabetes Association.