The relationship of vitamin D and parathormony level and microvascular complications in patients with diabetes mellitus

Introduction: Vascular complications constitute a large part of the mortality and morbidity caused by diabetes. Vitamin D has important effects on glucose metabolism. Vitamin D contributes to insulin synthesis and plays a role in reducing peripheral resistance to insulin. In addition, while vitamin D suppresses renin angiotensin aldosterone system and reduces albuminuria, it also has anti-inflammatory effects, immunomodulatory and cell proliferation regulatory effects. However, the relationship of vitamin D deficiency and developing secondary hyperparathyroidism with microvascular complications is not clear. In this study, we aimed to evaluate the relationship of vitamin D and parathormone (PTH) levels with diabetic neuropathy, retinopathy and nephropathy. Materials and Methods: 510 patients over 18 years of age with Diabetes Mellitus were included in this cross-sectional study. Clinical information was evaluated and laboratory results were obtained through examination of medical records. Patients were divided into three groups according to their vitamin D level as those with deficiency (vitamin D < 10 ng/mL), insufficiency (10 ng/mL ≤ vitamin D < 20 ng/mL), and those with adequate vitamin D (vitamin D ≥ 20 ng/mL). Parathormone level ≥88 pg/mL was defined as hyperparathyroidism. The rates of microvascular complications between groups were investigated. Results: When the patients were grouped according to their vitamin D levels, there was a statistically significant difference between the groups in terms of diabetic neuropathy and diabetic retinopathy, but there was no difference in terms of diabetic nephropathy. It was observed that the frequency of diabetic neuropathy and diabetic retinopathy decreased as the vitamin D level increased. When the patients were grouped according to PTH levels, there was a statistically significant difference between the groups in terms of diabetic neuropathy, but there was no difference in terms of diabetic retinopathy and diabetic neuropathy. It was observed that the incidence of diabetic neuropathy increased as the PTH level increased. It was determined that vitamin D was an independent predictor of diabetic retinopathy, and PTH was an independent predictor of diabetic nephropathy. Conclusion: Screening for vitamin D deficiency and providing vitamin D supplementation in diabetic patients may be beneficial both in providing blood sugar regulation and in preventing the development of diabetic neuropathy and diabetic retinopathy. Also, in clinical practice, in addition to vitamin D levels, PTH level monitoring in diabetic patients may provide additional benefit due to the relationship between PTH and diabetic neuropathy that we found in our study. There is a need for studies that will investigate the relationship between diabetes-related microvascular complications and vitamin D and PTH levels, and aim to reveal the cause-effect relationship. Keywords: Diabetes Mellitus, Vitamin D, Parathormone, Diabetic Microvascular Complications