Endocrine Abstracts

Introduction: Most of the human studies suggested an association between obesity and low 25(OH)D3 0levels. It has been proposed that co-existence of vitamin D deficiency may have a role in the development of IR in obesity. We aimed to reveal whether any association was present between IR and 25(OH)D3.

Materials-methods: 223 obese patients referred to our clinics were evaluated for the study. 24 patients with known diabetes mellitus were excluded. Finally, 199 patients were included and anthropometric (height, body weight, body mass index) and biochemical (fasting blood glucose, HbA1c) and hormonal (fasting insulin, C-peptide, 25(OH)D3) measurements were assessed. We evaluated IR by ‘homeostasis model assessment of IR’ (HOMA-IR). The patients having HOMA-IR value of equal to or greater than 2.5 were accepted as insulin resistant. The patients were grouped according to body mass index (BMI), HOMA-IR, and 25(OH)D3.

Results: 25(OH)D3 levels were significantly lower in the groups of BMI >50 kg/m² and BMI 40–50 kg/m² in comparison to the group of BMI<40 kg/m² (mean 25(OH)D3 levels 12.0, 12.12, 17.02 ng/dl; respectively) (P=0.042, P=0.025; respectively). BMI levels were significantly lower in the group of 25(OH)D3>30 ng/ml in comparison to the group of 25(OH)D3<10 ng/ml (mean BMI 42.27 vs 45.59 kg/m²; respectively) (P=0.05). Likewise, there was significant negative correlation between BMI and 25(OH)D3 (P=0.045, r=−0.142).There was no difference between 25(OH)D3 levels in patients with IR (HOMA≥2.5) and not IR (HOMA<2.5) patients (P=0.071). Similarly, there was no significant correlation between HOMA-IR values and 25(OH)D3 levels (P=0.98).

Conclusion: Our study showed that 25(OH)D3 levels decreased in obesity; and 25(OH)D3 levels were not different in patients having IR or not. These findings suggest that decreased vitamin D levels in obesity may be result of increasing BMI rather than IR.