Vitamin D Deficiency Is an Independent Risk Factor for Urinary Tract Infections After Renal Transplants

Vitamin D deficiency is frequently found in patients with renal transplants (RTxs). Because vitamin D plays indispensable roles in the immune system, there may be an association between vitamin D deficiency and infection in these patients, but this has not been fully elucidated. Therefore, this study investigated the impact of pre-RTx vitamin D deficiency on urinary tract infection (UTI) development after RTx.We measured 25-hydroxyvitamin D3 (25(OH)D3) levels in 410 patients 2 weeks before they underwent RTx. Vitamin D deficiency was defined as 25(OH)D3 <10 ng/mL. The primary outcome was UTI occurrence after RTx. Cox proportional hazard analysis determined whether vitamin D deficiency was independently associated with UTI.The mean 25(OH)D3 level was 12.8 ± 6.9 ng/mL, and 171 patients (41.7%) were vitamin D deficient. During a median follow-up duration of 7.3 years, the UTI incidence was significantly higher in vitamin D-deficient patients (52 patients, 30.4%) compared with vitamin D-nondeficient patients (40 patients, 16.7%) (P = 0.001). Moreover, multivariate Cox proportional hazard analysis showed that vitamin D deficiency was an independent predictor of UTI after RTx (hazard ratio 1.81, 95% confidence interval 1.11–2.97, P = 0.02).Vitamin D deficiency was an independent risk factor for UTI after RTx; hence, determining 25(OH)D3 levels might help to predict infectious complications after RTx.     

Optimum time to start antiretroviral therapy in patients with HIV-associated tuberculosis: before or after tuberculosis diagnosis?

WHO policy states that tuberculosis (TB) should be diagnosed and treated before starting antiretroviral treatment (ART). However, during the pre-ART screening period, diagnosing or excluding TB can be a lengthy process and may cause undesirable delays in ART initiation. In this observational study from South Africa, we report that initiation of ART before TB treatment in patients with delayed diagnoses of culture-positive prevalent TB was not associated with adverse clinical, immunological or virological outcomes during 12-month follow-up.     

Prevalence and associations of vitamin D deficiency in foreign-born persons with tuberculosis in London

OBJECTIVES: The incidence of tuberculosis (TB) is high amongst foreign-born persons resident in developed countries. Vitamin D is important in the host defence against TB in vitro and deficiency may be an acquired risk factor for this disease. We aimed to determine the incidence and associations of vitamin D deficiency in TB patients diagnosed at an infectious diseases unit in London, UK. METHODS: Case-note analysis of 210 unselected patients diagnosed with TB who had plasma vitamin D (25(OH)D3) levels routinely measured. Prevalence of 25(OH)D3 deficiency and its relationship to ethnic origin, religion, site of TB, sex, age, duration in the UK, month of 25(OH)D3 estimation and TB diagnosis were determined. RESULTS: Of 210 patients 76% were 25(OH)D3 deficient and 56% had undetectable levels. 70/82 Indian, 24/28 East African Asian, 29/34 Somali, 14/19 Pakistani and Afghani, 16/22 Sri Lankan and 2/6 other African patients were deficient (with 58, 17, 23, 9, 6 and 1 having undetectable levels, respectively). Only 0/6 white Europeans and 1/8 Chinese/South East Asians had low plasma 25(OH)D3 levels. Muslims, Hindus and Sikhs all had equivalent rates of deficiency though Hindus were more likely to have undetectable levels (odds ratio 1.87, 95% CI 1.27-2.76). There was no significant association between 25(OH)D3 level and site of TB or duration of residence in the UK. There was no apparent seasonal variation in either TB diagnosis or 25(OH)D3 level. CONCLUSIONS: 25(OH)D3 deficiency commonly associates with TB among all ethnic groups apart from white Europeans, and Chinese/South East Asians. Our data support a lack of sunlight exposure and potentially a vegetarian diet as contributors to this deficiency.     

Association of serum vitamin D levels with inflammatory response following hip fracture: the Baltimore Hip Studies

BACKGROUND: Vitamin D, known for its role in calcium homeostasis, may also regulate immune function. Whether vitamin D deficiency at the time of hip fracture is associated with the inflammatory response postfracture is not known. METHODS: In a cohort from the Baltimore Hip Studies, women aged >or= 65 years were evaluated at baseline and 2, 6, and 12 months after hip fracture repair. Serum at baseline was analyzed for 25-hydroxyvitamin D [25(OH)D], and serum from all time points was analyzed for interleukin-6 (IL-6). Participants were divided into two groups based on their baseline 25(OH)D levels. Vitamin D deficiency was defined as a 25(OH)D level of 相似文献   

Short Communication: Plasma Levels of Vitamin D in HIV Patients Initiating Antiretroviral Therapy Do Not Predict Immune Restoration Disease Associated with Mycobacterium tuberculosis

Abstract Immune restoration disease associated with Mycobacterium tuberculosis (TB IRD) is clinically important among HIV patients commencing antiretroviral therapy in countries where tuberculosis is endemic. Vitamin D affects dendritic cell and T cell function and the antimicrobial activity of monocytes. Plasma levels of vitamin D and polymorphisms in the vitamin D receptor may affect tuberculosis, and HIV infection associates with vitamin D deficiency. Here we assess whether plasma vitamin D levels may predict TB IRD. Samples were available from prospective studies of TB IRD in Cambodia (26 cases), India (19 cases), and South Africa (29 cases). IRD cases and controls from each site were similar in age and baseline CD4(+) T cell count. Plasma samples were assessed using 25(OH) vitamin D immunoassay plates. DNA samples were available from a subset of patients and were genotyped for the VDR FokI (F/f) [C/T, rs10735810] SNP. When data from each cohort were pooled to assess ethnic/geographic differences, 25(OH)D levels were higher in Cambodian than Indian or South African patients (p<0.0001) and higher in South African than Indian patients (p<0.0001). TB IRD was not associated with differences in levels of 25(OH)D in any cohort (p=0.36-0.82), irrespective of the patients' prior TB diagnoses/treatment. Carriage of the minor allele of VDR FokI (F/f) was marginally associated with TB IRD in Indian patients (p=0.06) with no association in Cambodians. Neither plasma levels of vitamin D nor the vitamin D allele will usefully predict TB IRD in diverse populations from TB endemic regions.     

Demographic characteristics and opportunistic diseases associated with attrition during preparation for antiretroviral therapy in primary health centres in Kibera, Kenya

Using routine data from HIV-positive adult patients eligible for antiretroviral therapy (ART), we report on routinely collected demographic characteristics and opportunistic diseases associated with pre-ART attrition (deaths and loss to follow-up). Among 2471 ART eligible patients, enrolled between January 2005 and November 2008, 446 (18%) were lost to attrition pre-ART. Adjusted risk factors significantly associated with pre-ART attrition included age <35 years (Odds Ratio, OR 1.4, 95% Confidence Interval, CI 1.1-1.8), severe malnutrition (OR 1.5, 95% CI 1.1-2.0), active pulmonary tuberculosis (OR 1.6, 95% CI 1.1-2.4), severe bacterial infections including severe bacterial pneumonia (OR 1.9, 95% CI 1.2-2.8) and prolonged unexplained fever (>1 month), (OR 2.6, 95% CI 1.3-5.2). This study highlights a number of clinical markers associated with pre-ART attrition that could serve as 'pointers' or screening tools to identify patients who merit fast-tracking onto ART and/or closer clinical attention and follow-up.     

The relationship between 25-hydroxyvitamin D levels and treatment course of pulmonary tuberculosis

BackgroundLow serum vitamin D level is associated with a high risk of developing active tuberculosis (TB). We investigated the relationships between serum vitamin D levels and clinical course of TB after standard chemotherapy in hospitalized non-HIV patients with TB.MethodsHospitalized patients with TB were recruited between February 2008 and July 2010. Confirmatory tests were performed using sputum smear and culture positivity tests for Mycobacterium tuberculosis. Drug sensitivity testing was performed for all the subjects and those not showing drug resistances for the first-line anti-TB drugs were included in the study. These patients were treated with the standard first-line anti-TB drugs. Serum 25-hydroxyvitamin D [25(OH)D] levels were measured on admission, and the relationships between 25(OH)D and clinical characteristics (laboratory data on admission and treatment outcomes) were examined. We defined vitamin D deficiency as a condition where serum level of 25(OH)D was lower than 20 ng/ml.ResultsA total of 38 patients were included in the study. Mean (±SD) 25(OH)D levels were 13.7±5.9 ng/ml. The prevalence of vitamin D deficiency was 87%. In 23 patients treated with the standard first-line 4-drug regimen (Age <80 years) serum 25(OH)D levels showed significant negative correlation with time taken to obtain 3 consecutive negative sputum smears or TB bacteria cultures. This relationship suggests that low serum vitamin D level may not only increase the risk of developing active TB but may also be related to the poor treatment outcomes in these patients.ConclusionsLow serum vitamin D level is a good predictor of prolonged clinical course in patients with active pulmonary TB.     

Risk factors for vitamin D deficiency in HIV-infected patients in the south central United States

We evaluated the prevalence of serum 25-hydroxyvitamin D [25(OH)D] deficiency and the risk factors for vitamin D deficiency in HIV-infected patients in the South-Central United States. The study consisted of a cross-sectional assessment of vitamin D levels in HIV-infected patients receiving routine clinical care from a private practice in Houston, Texas (latitude 29°N). Vitamin D deficiency was defined as 25(OH)D less than 20?ng/ml (<50?nmol/liter). Two-hundred enrolled patients were surveyed with a vitamin D questionnaire to determine daily supplemental vitamin D intake, dietary vitamin D intake, and average sunlight exposure (minutes/day). Multivariate logistic regression analysis was used to determine significant risk factors for vitamin D deficiency. Median 25(OH)D was 15.5?ng/ml (interquartile range 10.9-24.6) for the total population (n=200). Approximately, two-thirds (64%) of patients had vitamin D deficiency and 20.5% had severe vitamin D deficiency [25(OH)D <10?ng/ml or <25?nmol/liter]. In univariate analysis, African-American race, current tobacco use, increased body mass index (BMI), lower serum calcium level, no supplemental vitamin D use, and low daily supplemental and total daily vitamin D intake were significantly associated with vitamin D deficiency. In multivariate analysis, African-American race [adjusted odds ratio (AOR) 3.53 (95% confidence interval (CI) 1.83-6.82)], higher BMI [AOR 1.07 (95% CI 1.002-1.139)], and low daily vitamin D supplemental intake [AOR 0.997 (95% CI 0.996-0.999)] were significantly associated with vitamin D deficiency. No HIV factors including antiretroviral class use were significantly associated with either vitamin D deficiency or severe vitamin D deficiency. Vitamin D deficiency and severe vitamin D deficiency were highly prevalent in this HIV population. In the HIV population, African-Americans or patients with a high BMI may benefit from vitamin D supplementation.     

Seasonal changes in the biochemical indices of vitamin D deficiency in the elderly: a comparison of people in residential homes, long-stay wards and attending a day hospital

The seasonal changes in the biochemical indices of vitamin D nutrition have been measured in elderly people with differing requirements for institutionalized care. Residents of local authority homes (LAH) showed an increase in serum 25-hydroxyvitamin D3 [25(OH)D3] between spring and autumn (means 14-17 nmol/l, P less than 0.002). No significant seasonal changes were seen in patients on long-stay wards [(GW) serum 25(OH)D3 9.5 and 9.5 nmol/l] and in day-hospital attenders [(GDH) 25 and 26.8 nmol/l]. Significant differences (P less than 0.02 to P less than 0.0001) were found between the mean serum 25(OH)D3 amongst the three groups. A significant linear relationship (r = 0.84, P = 0.036) was found between mean serum 25-hydroxyvitamin D2[25(OH)D2] and dietary vitamin D2. The intake of vitamin D was suboptimal in all groups. The incidence of 25-hydroxyvitamin D deficiency [25(OH)D less than 12.5 nmol/l] varied from 11.7% of residents in LAH in autumn to 47% of GW patients in spring; but hypocalcaemia occurred less often (LAH 1.3% in autumn, GW 4.7% in spring). The diet assumes a greater role in protecting against vitamin D deficiency when the total 25(OH)D is low. Because most diets contain insufficient amounts of vitamin D, elderly institutionalized people will remain at high risk of developing vitamin D deficiency unless specific preventative measures are adopted.     

Effects of a Single,High Oral Dose of 25‐Hydroxycholecalciferol on the Mineral Metabolism Markers in Hemodialysis Patients

Vitamin D deficiency is common in dialysis patients with chronic kidney disease. Low levels have been associated with increased cardiovascular risk and mortality. We evaluated the administration of a high, single oral dose of 25‐OH cholecalciferol (3 mg of Hidroferol, 180 000 IU) in patients on chronic hemodialysis. The 94 chronic hemodialysis patients with vitamin D deficiency 25 (OH)D <30 ng/mL included in the study were randomized into two groups. Follow‐up time was 16 weeks. Neither the usual treatment for controlling Ca/P levels nor the dialysis bath (calcium of 2.5 mEq/L) were modified. Of the 86 patients who finished the study, 42 were in the treated group and 44 in the control group. An increase in 25(OH)D levels was observed in the treated group that persisted after 16 weeks and was associated with a significant decrease in parathyroid hormone (PTH) levels during the 8 weeks post‐treatment. Baseline 1,25(OH)₂D levels of the treated group increased two weeks after treatment (5.9 vs. 21.9 pg/mL, P < 0.001) but gradually reduced to 8.4 at week 16. The administration of a single 3 mg dose of 25‐OH cholecalciferol seems safe in patients on hemodialysis and maintains sufficient levels of 25(OH)D with a decrease in PTH for 3 months.     

Effects of vitamin D supplementation on circulatory YKL-40 and MCP-1 biomarkers associated with vascular diabetic complications: A randomized,placebo-controlled,double-blind clinical trial

AimDiabetic patients predispose to vascular diseases such as nephropathy, and retinopathy. Poor adherence to medical treatment and dietary recommendations in uncontrolled diabetes leads to vascular damages. Vitamin D has been extensively studied and found to be protective against diabetes mellitus. YKL-40 and Monocyte chemoattractant protein-1 (MCP-1) are considered to exert crucial role in diabetes and its complications. Therefore, this study was designed to investigate effects of vitamin D supplementation on serum levels of YKL-40 and MCP-1 involved in the development of diabetic complications.MethodsFor 12 weeks, 48 type 2 diabetic patients enrolled in the trial and randomly were divided into two groups (n = 24 per group), receiving one of the following: 100 μg (4000 IU) vitamin D or placebo. Before and after intervention, serumYKL-40, MCP-1, insulin, IL-6, TNF-α, 25- (OH) vitamin D and HbA1c were measured.ResultsOur results revealed that serum levels of 25 (OH) vitamin D significantly increased in vitamin D group (p < 0.001). Vitamin D supplementation also significantly reduced serum YKL-40 levels (−22.7 vs. −2.4 ng/ml; (p-value = 0.003)). There was a significant decline in MCP-1 concentration in intervention group at the end of the study (−45.7 vs. −0.9 pg/ml; (p = 0.001)). Furthermore, there was a significant decrease in IL-6, fasting insulin and HOMA-IR in intervention group after 3 months supplementation.ConclusionsDaily vitamin D supplementation effectively reduced circulatory YKL-40 and MCP-1 levels in patients with type-2 diabetes and vitamin D deficiency. Vitamin D might contribute in reducing diabetic complications via modulating YKL-40 and MCP-1 signaling pathways.     

Vitamin D deficiency in children and adolescents with type 1 diabetes

Objective: To investigate the frequency and effects of vitamin D deficiency in children with type 1 diabetes (T1D) in a region which is known to have a high rate of vitamin D deficiency among adolescents. Methods: In this prospective cross-sectional study, 120 children and adolescents with T1D (55 girls and 65 boys) aged 3-20 years were evaluated. Serum 25-hydroxyvitamin D [25(OH)D], parathormone (PTH), and alkaline phosphatase (ALP) levels were measured. Hemoglobin A1c levels and daily insulin requirement were also evaluated. Classification of vitamin D status was made according to the American Academy of Pediatrics (AAP)/LWEPS’s recommendations. The patients were divided into 2 groups according to their vitamin D status and also according to the season of the year in which 25(OH)D sampling was done. Results: Serum 25(OH)D levels revealed vitamin D deficiency or insufficiency in 38% of the patients. Higher PTH levels were found in the patient group whose mean 25(OH)D level was <20 ng/mL as compared to the group whose mean 25(OH)D level was >20 ng/mL (p<0.05). Only 11% of patients had secondary hyperparathyroidism. The 25(OH)D levels of patients whose serum samples were taken in summer and spring months were significantly different (p<0.05). There were no significant correlationsbetween 25(OH)D level and daily insulin dose. Conclusion: Although we could not show a significant association between vitamin D deficiency and metabolic parameters, the frequency of vitamin D deficiency in T1D children is substantial. Vitamin D status should be assessed also in patients who do not have signs of rickets.Conflict of interest:None declared.     

25-hydroxyvitamin D deficiency in renal transplant recipients

CONTEXT: Bone disease after kidney transplantation is a common problem. The serum levels of the active vitamin D metabolite 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D] have been studied extensively. In contrast, there has not been much concern about the serum levels of 25-hydroxyvitamin D(3) [25(OH)D]. However, it is well recognized that serum levels of 1,25(OH)(2)D are often normal in vitamin D-deficient patients. Moreover, inadequate serum 25(OH)D may limit the extrarenal production of 1,25(OH)(2)D that could lead to increased risk of many chronic diseases. OBJECTIVE: We analyzed whether renal transplant patients were at a higher risk of 25(OH)D deficiency because of the consequence of their need to protect themselves from sun exposure. DESIGN, SETTING, AND PATIENTS: We hypothesized that renal transplant recipients are at high risk to develop 25(OH)D deficiency. Serum 25(OH)D levels were analyzed in renal transplant patients with adequate renal function and in an age- and gender-matched control group (n = 31) at the end of winter. All renal transplant patients practiced solar UV-protection after transplantation. 25(OH)D levels were compared using a nonparametrical test (Wilcoxon rank sum test). RESULTS: Serum 25(OH)D levels were significantly lower in renal transplant patients compared with controls (P = 0.007). Geometric mean (with 95% confidence interval) in renal transplant patients was 10.9 ng/ml (8.2-14.3) compared with 20.0 ng/ml (15.7-25.5) in the control group. CONCLUSIONS: Renal transplant recipients are at high risk to develop 25(OH)D deficiency. Treatment with vitamin D is recommended to correct their vitamin D deficiency, which may help protect them from serious vitamin D deficiency-related health problems that include an increased risk for internal malignancies.     

High prevalence of vitamin D deficiency in Japanese female patients with Graves' disease

We reported previously that vitamin D deficiency is a causal mechanism of postoperative tetany in patients with Graves' disease. The aim of the present study was to determine the prevalence of vitamin D deficiency by reviewing serum 25(OH)D levels in 208 patients with Graves' disease (146 women, 62 men) during a 1 year period. Serum 25(OH)D levels were significantly lower (p < 0.001) in female Graves' patients (31.8 +/- 13.3 nmol/l) than in male patients (41.3 +/- 15.0 nmol/l). Vitamin D deficiency (defined as a serum 25(OH)D value below 25 nmol/l) was found in 40% of female patients and in 18% of male patients (p < 0.005). There was a significant seasonal variation in the 25(OH)D concentrations in female patients [amplitude 6.38 (95% CI, 5.42-7.56)], with values below 25 nmol/l found in 58% of female patients during the winter months. There were significant (p < 0.001) differences in serum 25(OH)D levels between age groups in the female patients. The concentrations were lowest in patients in their twenties (25.1 +/- 8.2 nmol/l) and highest in patients in their fifties and sixties (43.2 +/- 13.7 nmol/l). Serum 25(OH)D concentrations might be monitored in patients with Graves' disease during antithyroid drug therapy, and vitamin D and/or calcium supplements are recommended for patients with vitamin D deficiency.     

Vitamin D deficiency in Crohn's disease: Prevalence,risk factors and supplement use in an outpatient setting

Background and aimsVitamin D deficiency impacts on bone health and has potential new roles in inflammation. We aimed to determine the prevalence of and risk factors for vitamin D deficiency and to explore vitamin D supplement usage in patients with Crohn's disease (CD) in an outpatient setting, compared with controls.MethodsSerum 25-hydroxyvitamin D [25(OH)D] concentrations were measured by radioimmunoassay in 151 participants, comprising 81 CD patients and 70 age-, sex- and socio-economic status-matched healthy controls. Levels of 25(OH)D < 50 nmol/L were classed as deficient. Data on vitamin supplement usage were recorded for all participants at interview.ResultsVitamin D deficiency was common in patients with CD (63%) and significantly higher in winter than summer (68% v 50%; p < 0.001, χ²). Notably, the deficiency rate remained high even in summer (50%). On regression analysis, 25(OH)D levels were inversely associated with winter season. Disease-specific factors for lower serum 25(OH)D levels were longer disease duration and smoking. Overall, 43% of patients reported using a vitamin D-containing supplement, primarily at low dosages (200–400 IU/d); however, this level of supplement did not prevent deficiency. For the majority of CD patients, 25(OH)D remained below optimal levels proposed to confer bone and immune health benefits.ConclusionsVitamin D deficiency was common in patients with CD and associated with longstanding disease, smoking and winter. While over 40% of patients used a vitamin D-containing supplement, the dosages were inadequate to prevent deficiency. Appropriate vitamin D screening and supplementation should be considered in the context of health promotion of outpatients with CD.     

Investigating the Efficiency of Vitamin D Administration with Buccal Spray in the Treatment of Vitamin D Deficiency in Children and Adolescents

Objective:The aim of this study was to evaluate the efficiency of a buccal spray form of vitamin D compared to single oral dose (stoss therapy) and oral drops therapy in the treatment of vitamin D deficiency.Methods:Ninety healthy children and adolescents (3-18 years) with vitamin D deficiency [serum level of 25-hydroxyvitamin D (25(OH) D) <12 ng/mL] were randomized to receive vitamin D3 buccal spray (2000 U, n=30, group 1) for six weeks, oral drops (2000 U, n=30, group 2) for six weeks and a single oral dose (300 000 U) vitamin D3 (n=30, group 3). Serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone and 25(OH)D levels of the patients were measured at baseline and after the treatment on the 42^nd day.Results:All three groups had a significant increase in serum 25(OH)D concentrations (p<0.001). In group 1, baseline mean 25(OH)D was 8.0±0.41 ng/mL, which rose to 22.1 (17.8-28.2) ng/mL after treatment with a mean increase of 15.6±1.3 ng/mL. Similarly in group 2, baseline, post-treatment and mean increase in 25(OH)D concentrations were 7.9±0.45 ng/mL, 24.4 (20.6-29.6) ng/mL and 17.3±1.1 ng/mL while for group 3 these values were 7.6±0.47 ng/mL, 40.3 (29.4-58.4) ng/mL and 34.3±3.2 ng/mL, respectively.Conclusion:We conclude that vitamin D3 supplementation with buccal spray and oral drops is equally effective in terms of raising vitamin D concentrations in short-term treatment of vitamin D deficiency.     

Vitamin D deficiency and its association with disease activity in new cases of systemic lupus erythematosus

Evidence has shown a relationship between vitamin D deficiency and systemic lupus erythematosus (SLE). We evaluated the frequency of vitamin D deficiency and its association with disease activity in new cases of SLE. Women with newly diagnosed SLE, based on the American College of Rheumatology (ACR) criteria, were enrolled consecutively. Those receiving vitamin D supplements and postmenopausal women were not included. Disease activity was measured by the BILAG index (2004) and serum concentration of 25-hydroxyvitamin D (25[OH]D) was measured by radioimmunoassay method. Forty SLE patients with mean age of 25.3?±?4.2 years were studied. Severe, moderate, and mild vitamin D deficiency, corresponding to serum 25[OH]D concentrations of <12.5, 12.5-24.9, and 25-39.9 nmol/l, were found in 12.5%, 62.5%, and 17.5% of the patients, respectively. Serum 25[OH]D concentration was inversely correlated with the British Isles Lupus Assessment Group (BILAG) index score (r?=?-0.486, p?=?0.001). Those with a more severe vitamin D deficiency had also higher concentrations of liver enzymes (p?相似文献   

Reciprocal seasonal variation in vitamin D status and tuberculosis notifications in Cape Town, South Africa

Vitamin D deficiency is associated with susceptibility to tuberculosis (TB) in HIV-uninfected people in Europe, but it is not known whether such an association exists among HIV-infected people in subtropical Africa. We conducted a cross-sectional study to determine whether vitamin D deficiency was associated with susceptibility to active TB in HIV-uninfected (n = 196) and HIV-infected (n = 174) black Africans in Cape Town, South Africa. We also investigated whether there was evidence of seasonal variation in vitamin D status and TB notifications in this setting over an 8-y period. Vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] <50 nmol/L) was present in 232 (62.7%) of 370 participants and was associated with active TB in both HIV-uninfected (odds ratio = 5.2, 95% confidence interval: 2.8-9.7; P < 0.001) and HIV-infected (odds ratio = 5.6, 95% confidence interval: 2.7-11.6; P < 0.001) people. Vitamin D status varied according to season: The mean serum 25(OH)D concentration was highest in January through March and lowest in July through September (56.8 vs. 30.7 nmol/L, respectively; P < 0.001). Reciprocal seasonal variation in TB notifications was observed: The mean number of TB notifications per quarter for Cape Town in 2003 to 2010 was lowest in April through June and highest in October through December (4,222 vs. 5,080; P < 0.001). Vitamin D deficiency is highly prevalent among black Africans in Cape Town and is associated with susceptibility to active TB both in the presence and absence of HIV infection. Reciprocal seasonal variation in serum 25(OH)D concentration and TB notifications suggests that seasonal variations in vitamin D status and TB incidence in this setting are causally related.     

Vitamin D: synthesis, metabolism, regulation, and an assessment of its deficiency in patients with chronic renal disease

The main source of vitamin D in a man is its synthesis in human skin. 7-Dehydrocholesterol converts into cholecalciferol--vitamin D3--as a result of UV radiation. Cholecalciferol hydroxylates in liver into 25-hydroxyvitamin D3 [25(OH)D, calcidiol], which concentration in blood is a relevant indicator of the total of vitamin D in a human body. 25(OH)D hydroxylates in kidneys into 1,25-dihydroxyvitamin D3 [1,25(OH)2D, calcitriol], which is considered an active metabolite of vitamin D. Epidemiological studies showed high prevalence of low concentrations of 25(OH)D especially in older population and people with chronic diseases. 25(OH)D concentrations were defined at which rise parathormone levels, increases bone conversion, impairs bone mineralization and develops osteomalacia. Based on these results a deficiency of vitamin D was defined. Patients with chronic renal disease experience development of serious bone impairments described as renal osteodystrophy. These disorders are caused by secondary hyperparathyroidism which develops as a result of mineral metabolism impairment, especially of hypocalemia, 25(OH)D deficiency, and insufficient synthesis of 1,25(OH)2D. Presently published guidelines K/DOQI Clinical Practice Guidelines for Chronic Kidney Disease: Evaluation, Classification and Stratification define processes of vitamin D supplementation, particularly 1,25(OH)2D according to a degree of renal disease. Early prevention and treatment of hypovitaminosis D is a treatment goal in order to reduce or stop development of secondary hyperparathyroidism with its consequences for bone metabolism.