Study on the correlation between serum vitamin D level, parathyroid hormone and type 2 diabetes mellitus in Inner Mongolia / 中华临床营养杂志

ABSTRACT

Objective:To evaluate the correlation of serum vitamin D (VitD) and parathyroid hormone (PTH) with insulin resistance and islet β-cell function in patients with type 2 diabetes mellitus (T2DM), and to analyze the role of serum VitD and PTH in the progression of T2DM.Methods:A total of 376 T2DM patients hospitalized in endocrinology department from January 2018 to January 2021 were selected. The baseline data were collected and the biochemical indexes were determined. Patients were divided into 3 groups according to serum VitD level, including 220 cases in deficiency group [25-(OH)D ≤ 20 μg/L], 107 cases in insufficiency group [25-(OH)D>20 and ≤ 30 μg/L] and 49 cases in sufficiency group [25-(OH)D > 30 μg/L]. Meanwhile, 31 of the patients were classified into PTH decreased group (PTH < 25.16 ng/L), 137 into normal PTH group (PTH ≥ 25.16 and < 38.35 ng/L) and 208 into PTH elevated group ( PTH ≥ 38.35 ng/L). According to body mass index (BMI), patients were divided into normal weight group (18.5 kg/m 2 ≤ BMI ≤ 23.9 kg/m 2), overweight group (BMI ≥24 and ≤ 27.9 kg/m 2) and obese group (BMI ≥ 28 kg/m 2). Results:Among the three groups defined by serum VitD level, comparisons of glucose metabolism and calcium and phosphorus metabolism indicators showed no significant differences in BMI, fasting insulin (FINS), fasting plasma glucose (FPG), homeostasis model assessment of insulin resistance index (HOMA-IR), serum calcium and phosphorus (all P > 0.05). The levels of glycated hemoglobin (HbA1c) and PTH in vitamin D deficiency group and sufficiency group were significantly lower compared with vitamin D deficiency group (both P < 0.05). Among the three groups defined by PTH level, there were no significant differences in BMI, FINS, FPG, HbAlc, HOMA-IR, and serum calcium (all P > 0.05). Serum phosphorus in the PTH elevated group was significantly lower compared with PTH decreased and normal PTH group ( P = 0.000), and VitD in the PTH elevated group was significantly lower compared with PTH decreased group ( P = 0.002). There were significant differences in age and blood phosphorus among the three groups defined by BMI level (all P<0.05). According to the analysis of clinical indexes of different nationalities, the level of VitD in Mongolians was significantly higher than that in Han nationality patients ( P <0.034). Spearman correlation analysis showed that VitD was negatively correlated with PTH and HOMA-IR and positively correlated with serum calcium. PTH was negatively correlated with serum calcium and phosphorus, and positively correlated with HOMA-IR. There was a significant negative correlation between normal PTH and VitD. Multiple linear regression analysis showed that HOMA-IR and homeostasis model assessment of β-cell function (HOMA-β) were protective factors, and FPG and FINS were risk factors for HOMA-IR and HOMA- β. Conclusion:There is a negative correlation between VitD and insulin resistance, and a positive correlation between PTH and insulin resistance, suggesting that VitD and PTH are possibly two impacting factors for T2DM pathogenesis.