Vitamin D is a neuro-hormone regulating calcium-phosphate homeostasis. However, vitamin D deficiency has been reported in several chronic conditions associated with increased inflammation and dysregulation of the immune system such as Type 1 Diabetes (T1D), autoimmune thyroiditis, autoimmune gastritis. The role of autoimmune gastritis in the pathogenesis of nutritional deficiencies has been revealed, therefore we assumed a possible association between gastric Parietal Cells Autoantibodies (PCA) and 25(OH)D deficiency in T1D patients. The aim of this study was to evaluate the prevalence of 25(OH)D deficiency in patients with T1D and vitamin D status association with PCA. We also assessed the prevalence of Thyroid Peroxidase Autoantibodies (TPOAb) in T1D patients and its potential influence on vitamin D status. 

Methods: 78 T1D patients (42 females; mean age 43.5 ± 12.8 years) were followed-up in endocrinology research centre from December 2017 to May 2019. 25(OH)D, parathormone, calcium, PCA, TPOAb were measured in all T1D patients. We also evaluated autoantibodies to Glutamic Acid Decarboxylase (GAD), Islet Antigen 2 (IA2) and Zinc Transporter Isoform-8 (Znt8) to confirm the autoimmune genesis of diabetes. The results were compared with a control group of 42 healthy subjects.

Results:  In T1D group (n=78) 25(OH)D levels were significantly lower than in the control group 14,6 [9,1;23,0] vs. 27,0 [22,1; 34,7] ng/ml, p < 0,0001. 29 out of 78 patients with T1D were positive to PCA. Vitamin D values in these groups were 17,3 [9.9 23.6] and 12 ,4 [7,1;23,0] respectively. 

Only 3 out of 42 patients (7%) were positive to PCA in control group without autoimmune diseases.

It is noteworthy that T1D patients with TPOAb (30 out of 78may patients) had lower 25(OH)D values as compared to those without TPOAb (44 patients) - 11,8 [6,8; 22,1 ] vs 20 [11,1; 26,7] ng/ml; p = 0,0047. 

Conclusion:  Data from the present study showed a significant reduction of 25(OH)D levels in T1D patients. No meaningful difference in vitamin D status was found in patients with and without PCA. Possible impairment of vitamin D absorption in autoimmune gastritis may be caused by mucosal atrophy which may appear years after PCA start to be detectable in blood. TPOAb in T1D patients may have an impact on vitamin D deficiency in such patients.

TBA