Association of Serum 25-Hydroxyvitamin D Level with 1,25-Dihydroxyvitamin D Deficiency in End Stage Renal Disease Patients Referred to 5th Azar Hospital of Gorgan

25(OH)D is decreased in the patients with end stage renal disease (ESRD). Some evidences are available showed that 25(OH)D measurement can reflected the serum levels of active form of vitamin D [1,25(OH)2D] in ESRD patients. The aim of this study was to assess the association of serum 25-hydroxyvitamin D levels with 1,25-dihydroxyvitamin D deficiency in end stage renal disease patients (1, 2). The hormones related to vitamin D are calcitonin and parathyroid hormone, all of which are involved in renal calcium reabsorption (3). Vitamin D production is stimulated by parathyroid hormone and decreased by calcium. Extrarenal synthesis of vitamin D occurs under the influence of cytokines and is essential for paracrine regulation and cell differentiation (4). Plasma concentrations of 1 and 25-hydroxyvitamin D (1,25 (OH) 2D) in plasma are constantly monitored by parathyroid hormone (PTH), serum calcium and phosphate, and fibroblast-like growth factor 23. Low levels of 1,25 (OH) 2D are observed even in the early stages of kidney failure. Decreased levels of 1,25 (OH) 2D are exacerbated by the progression of renal failure (5). Deficiency in the production of 1-alpha hydroxylase enzyme in renal failure is thought to be the main mechanism of this process. However, phosphate retention and FGF-23 have also been attributed to reduced synthesis of 1,25 (OH) 2D. However, phosphate retention and FGF-23 have also been attributed to reduced synthesis of 1,25 (OH) 2D. In addition, hyperphosphatemia, metabolic acidosis, and other uremic toxins may suppress 1-alpha hydroxylase activity and 1,25 (OH) 2D synthesis, but its effects in advanced stages of chronic kidney disease (CKD) such as stages 4 and 5 Reaches the maximum (6, 7). Due to the fact that studies have shown that replacing vitamin D deficiency with active drug forms D2 and D3 is more effective and potency than inactive forms of vitamin D, and these compounds suppress the increase of serum PTH and thus the side effects and pain. Therefore, the aim of this study was to investigate the relationship between serum levels of 25-hydroxyvitamin D (25 (OH) D) and deficiency of 1 and 25-hydroxyvitamin D (1,25 (OH) 2D) in patients. The final stage was kidney disease (ESRD).

This study is descriptive-analytical and cross-sectional. The study population included all patients with end-stage renal disease referred to the Panj Azar Educational and Medical Center in Gorgan during 2014. Based on the study of Urena et al. In 2011 (20) and estimating the correlation coefficient of 0.29 for the linear relationship between serum level of -25-hydroxyvitamin D with 1 and -25-hydroxyvitamin D in ESRD patients and the following relationship at the significant level of 0.05 and Test power was 80%, sample size was calculated to be 91 people. In this study, 88 ESRD patients referred to 5th Azar Hospital in Gorgan in 2014 were studied. After recording demographic data, the serum levels of 25(OH)D and 1,25(OH)2D and other laboratory parameters were measured. Collected data were analyzed by SPSS-18 statistical software and chi-square and t tests and Pearson’s correlation model. This study was approved by the ethics committee of Golestan University of Medical Sciences with ethics code IR.GOUMS.REC 31078693122416. Blood samples from all patients up to 10 cc for routine tests of patients with renal failure including CBC, Na, K, Ca, P, BUN, Cr, PTH and ALP and in the next step to measure serum level 25 - Hydroxyvitamin D as well as 1 and 25-hydroxyvitamin D were performed. Vitamin D was measured by ELISA method with a special kit. Serum levels of 25-hydroxyvitamin D less than 15-30 ng / ml were considered as insufficient vitamin D, values ​​less than 15 ng / ml were considered as vitamin D deficiency and high values ​​above 30 ng / ml were considered normal. And outside this range was considered abnormal. The range of normal values ​​of 1 and 25-hydroxyvitamin D was determined in a large study of 20-60 pg / ml (4). Inclusion criteria included end-stage renal disease and non-inclusion criteria were not receiving vitamin D supplements during the last month. The researcher asked all the patients included in the study about not taking vitamin D and if they did not take it, they entered the study. Dialysis adequacy factor is calculated by the formula KT / V, which was calculated monthly in the forms of dialysis patients in the 5 Azar Medical Center, and in fact, a number less than 1.5 was considered as the optimal dialysis adequacy. The sun-damaging factor was removed so that all samples were collected in one season, and all patients received normal community nutrition. The collected data were analyzed after coding and entry in SPSS software version 18. Mean, median, standard deviation and percentage were used to describe the data. If the serum levels of vitamin D were normal, t-test was used to compare the mean serum levels of vitamin D between groups (insufficient amounts, deficiency and normality of vitamin D). Chi-square test (2 χ) was used to compare the ratio of vitamin deficiency between groups and Pearson correlation test was used to compare numerical variables. If the data were not normal, non-parametric tests were used. The significance level of the tests was considered 0.05.

The mean age of patients was 56.1±14.1 years and 43.2% of them were male and 56.8% were female. 51.1% of patients were obese or overweight. The mean serum concentrations of 25(OH)D and 1,25(OH)2D were 23.3±16.7 and 147.3±49.2 ng/dl, respectively. Moreover, 51.1% of them had 25(OH)D deficiency, 44.3% insufficiency and 4.5% sufficiency. 1.1% of patients had 1,25(OH)2D deficiency and 98.9% had increased 1,25(OH)2D. 25(OH)D serum levels in ESRD patients were associated with 1,25(OH)2D serum levels (P=0.037). There was no association between vitamin D serum concentrations and studied variables (P>0.05).

The results of this study showed that 25(OH)D serum level had a negative and significant correlation with 1,25(OH)2D serum level.