Introduction and objective: The aim of this study has been to evaluate the relationship between vitamin D and iPTH levels and the status of carbohydrate metabolism in a representative sample of the Spanish population.
Material and methods: The study was conducted in two population of northern and southern Spain, evaluated in the same period of time and with a similar methodology: Pizarra Study (Málaga) and Asturias Study. Subjects in both groups underwent clinical and anthropometric assessment survey, a blood test (fasting glucose and insulin, creatinine, calcium, phosphorus, 25OH vitamin D, iPTH) homeostatic model assessment-insulin resistance (HOMA-IR) and an oral glucose tolerance test (OGTT). The number of subjects included was 1182. To calculate the statistical difference between the means of continuous variables we used the ANOVA test for quantitative and the χ2 test for qualitative variables. Strength of association between two variables was measured using odds ratio (OR).
Results: The mean age of participants was 50.3±14.4 years (range: 2083 years), with 57% female and 43% male. The mean of 25-hydroxyvitamin D and iPTH were: 22.46 ng/ml and 42.29 pg/ml, respectively. 65.6% had normal fasting glucose and OGTT, 6.45% impaired fasting glucose, 8.15% carbohydrate intolerance, 9.85% new diagnosed diabetes and 9.93% known diabetes.25-hydroxyvitaminD levels in these groups were, respectively: 23.43, 21.45, 22.97, 21.82 and 23.22 (P 0.034) and iPTH: 45.1, 48.26, 45.99, 49.31 and 41.08 (P 0.001) both adjusted for age, sex, BMI and season. The percentage of patients with 25-hydroxyvitaminD levels below 20 ng/ml was different in the five groups: 30.9, 35.5, 37.5, 49.1 and 36.8% (P 0.014).Vitamin D levels were significantly different for different values of HOMA-IR: quartile 1 (HOMA<1.07): 25.85; quartile 2 (HOMA 1.071.73): 22.94; quartile 3 (1.742.95): 22.54 and quartile 4 (>2.95): 22.05 (P0.041, all adjusted for age, sex, BMI and season).
Conclusions: 1-One-third of the subjects studied have 25hydroxyvitaminD levels below 20 ng/ml,
2-The higher the insulin resistance (HOMA-IR) the lower the levels of vitamin D,
3-Patients with undiagnosed diabetes have 25hydroxyvitaminD levels significantly lower and iPTH significantly higher than normal population.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.