Vitamin D deficiency is common among Polish children with newly diagnosed type 1 diabetes mellitus.

Introduction: In recent years, the prevalence of T1DM (type 1 diabetes mellitus) and other autoimmune diseases in the paediatric population has been increasing. The aim of this study was to evaluate vitamin D levels among children with newly diagnosed T1DM, taking into account the most common coexisting autoimmune conditions.

Material and methods: The database included 361 patients diagnosed with T1DM between 2020 and 2021, with a mean age of 9.27 ± 4.1 years, 189 boys. Auxological data and biochemical results of routinely performed tests were retrospectively analysed: blood pH and bicarbonate (HCO3-) on gasometry on admission, glycated haemoglobin (HbA1c), levels of antibodies against glutamic acid decarboxylase (GAD), antibodies against tyrosine phosphatase (IA2), antibodies against zinc transporters (ZnT8), 25-hydroxy vitamin D (25(OH)D), anti-IgA tissue transglutaminase antibodies (TTG-IgA), total IgA, levels of antibodies against thyroperoxidase (TPOAb), and antibodies against thyroglobulin (TgAb).

Results: 35.5% of children (n = 128) with T1D presented 25(OH)D deficiency (< 20 ng/mL), 37% (n = 134) had suboptimal levels (20-30 ng/mL), and 25% (n = 90) had optimal vitamin D levels (30-50 ng/mL). 25(OH)D values were inversely proportional to the severity of diabetic ketoacidosis (p < 0.01) and negatively correlated with HbA1c values (p < 0.05). 25(OH)D levels were also found to be negatively correlated with children's age at diagnosis (p < 0.001). Statistical analysis showed no association between 25(OH)D value and body mass index (BMI) Z-score or type of antibodies typical of T1D. There was also no statistically significant difference in vitamin D levels among patients with additional autoimmune processes (antibodies to thyroperoxidase and/or thyroglobulin and antibodies to tissue transglutaminase).

Conclusions: More than one-third of Polish children with newly diagnosed T1D have 25(OH)D deficiency, especially in patients with diabetic ketoacidosis (DKA) at the diagnosis of diabetes. Determination of vitamin D levels should be a routine procedure in children with newly diagnosed T1DM.