Hypercalcémie majeure secondaire à une intoxication par la vitamine D

Vitamin D and Cardiovascular Diseases: An Update

Vitamin D is a vital nutrient that plays a significant part in several physiological processes within the human body, including calcium metabolism, bone health, immune function, and cell growth and differentiation. It is obtained mainly through exposure to sunlight but can be acquired from certain foods and supplements as well. Vitamin D deficiency (VDD) could be the risk factor for cardiovascular diseases (CVDs), such as heart disease and stroke. In blood vitamin D low levels have been linked with an enhanced risk of developing CVDs. However, it is unclear whether vitamin D levels are the leading cause or consequence of these conditions. While some studies highlight that taking vitamin D supplements could decrease the risk of CVD; however, more research is required to better understand the association between vitamin D and cardiovascular health. In this review, we aimed to summarize the currently available evidence supporting the association between vitamin D and CVDs and anesthesia considerations.

Vitamin D: sources, physiological role, biokinetics, deficiency, therapeutic use, toxicity, and overview of analytical methods for detection of vitamin D and its metabolites

Vitamin D has a well-known role in the calcium homeostasis associated with the maintenance of healthy bones. It increases the efficiency of the intestinal absorption of dietary calcium, reduces calcium losses in urine, and mobilizes calcium stored in the skeleton. However, vitamin D receptors are present ubiquitously in the human body and indeed, vitamin D has a plethora of non-calcemic functions. In contrast to most vitamins, sufficient vitamin D can be synthesized in human skin. However, its production can be markedly decreased due to factors such as clothing, sunscreens, intentional avoidance of the direct sunlight, or the high latitude of the residence. Indeed, more than one billion people worldwide are vitamin D deficient, and the deficiency is frequently undiagnosed. The chronic deficiency is not only associated with rickets/osteomalacia/osteoporosis but it is also linked to a higher risk of hypertension, type 1 diabetes, multiple sclerosis, or cancer. Supplementation of vitamin D may be hence beneficial, but the intake of vitamin D should be under the supervision of health professionals because overdosing leads to intoxication with severe health consequences. For monitoring vitamin D, several analytical methods are employed, and their advantages and disadvantages are discussed in detail in this review.

Update of the tolerable upper intake level for vitamin D for infants

Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to revise the tolerable upper intake level (UL) for vitamin D for infants (≤ 1 year) set in 2012. From its literature review, the Panel concluded that the available evidence on daily vitamin D intake and the risk of adverse health outcomes (hypercalciuria, hypercalcaemia, nephrocalcinosis and abnormal growth patterns) cannot be used alone for deriving the UL for infants. The Panel conducted a meta-regression analysis of collected data, to derive a dose-response relationship between daily supplemental intake of vitamin D and mean achieved serum 25(OH)D concentrations. Considering that a serum 25(OH)D concentration of 200 nmol/L or below is unlikely to pose a risk of adverse health outcomes in infants, the Panel estimated the percentage of infants reaching a concentration above this value at different intakes of vitamin D. Based on the overall evidence, the Panel kept the UL of 25 μg/day for infants aged up to 6 months and set a UL of 35 μg/day for infants 6-12 months. The Panel was also asked to advise on the safety of the consumption of infant formulae with an increased maximum vitamin D content of 3 μg/100 kcal (Commission Delegated Regulation (EU) 2016/127 repealing Directive 2006/141/EC in 2020). For infants aged up to 4 months, the intake assessment showed that the use of infant formulae containing vitamin D at 3 μg/100 kcal may lead some infants to receive an intake above the UL of 25 μg/day from formulae alone without considering vitamin D supplemental intake. For infants aged 4-12 months, the 95th percentile of vitamin D intake (high consumers) estimated from formulae and foods fortified or not with vitamin D does not exceed the ULs, without considering vitamin D supplemental intake.

The identification of nuclear receptors associated with hepatic steatosis to develop and extend adverse outcome pathways

The development of adverse outcome pathways (AOPs) is becoming a key component of twenty-first century toxicology. AOPs provide a conceptual framework that links the molecular initiating event to an adverse outcome through organized toxicological knowledge, bridging the gap from chemistry to toxicological effect. As nuclear receptors (NRs) play essential roles for many physiological processes within the body, they are used regularly as drug targets for therapies to treat many diseases including diabetes, cancer and neurodegenerative diseases. Due to the heightened development of NR ligands, there is increased need for the identification of related AOPs to facilitate their risk assessment. Many NR ligands have been linked specifically to steatosis. This article reviews and summarizes the role of NR and their importance with links between NR examined to identify plausible putative AOPs. The following NRs are shown to induce hepatic steatosis upon ligand binding: aryl hydrocarbon receptor, constitutive androstane receptor, oestrogen receptor, glucocorticoid receptor, farnesoid X receptor, liver X receptor, peroxisome proliferator-activated receptor, pregnane X receptor and the retinoic acid receptor. A preliminary, putative AOP was formed for NR binding linked to hepatic steatosis as the adverse outcome.

Vitamin D toxicity resulting from overzealous correction of vitamin D deficiency

BACKGROUND

Vitamin D toxicity, often considered rare, can be life-threatening and associated with substantial morbidity, if not identified promptly.

OBJECTIVE

To describe clinical and biochemical features, risk factors and management of patients with vitamin D toxicity seen between January 2011 and January 2013.

METHODOLOGY

Patients presenting with vitamin D toxicity, between January 2011 and January 2013, at single tertiary care centre in Delhi-NCR, India, were included. Evaluation included detailed clinical history and biochemical tests including serum calcium, phosphorus, creatinine, intact parathyroid hormone and 25-hydroxyvitamin D (25(OH)D).

RESULTS

Sixteen patients with vitamin D toxicity could be identified. Clinical manifestations included nausea, vomiting, altered sensorium, constipation, pancreatitis, acute kidney injury and weight loss. Median (range) age was 64·5 (42-86) years. Median (range) serum 25(OH)D level and median (range) serum total serum calcium level were 371 (175-1161) ng/ml and 13·0 (11·1-15·7) mg/dl, respectively. Overdose of vitamin D caused by prescription of mega-doses of vitamin D was the cause of vitamin D toxicity in all cases. Median (range) cumulative vitamin D dose was 3,600,000 (2,220,000-6,360,000) IU.

CONCLUSION

Our data demonstrate an emergence of vitamin D toxicity as an increasingly common cause of symptomatic hypercalcaemia. Irrational use of vitamin D in mega-doses resulted in vitamin D toxicity in all cases. Awareness among healthcare providers regarding the toxic potential of high doses of vitamin D and cautious use of vitamin D supplements is the key to prevent this condition.

Prolonged androgenic anabolic steroid (AAS) induced QT interval shortening: a suitable screening tool?

Androgenic anabolic steroid (AAS) abuse is associated with changes in cardiac electrophysiology. Recently heart rate corrected QT interval (QTc) has been suggested as a method of screening for AAS use in athletes despite conflicting reports. This study aimed to further investigate the effect of AAS on QTc in a cohort of long-term AAS users in whom the affects may be more pronounced. Using a cross-sectional cohort design with AAS using resistance trained athletes (AS n = 15) and a group of non-AAS using resistance trained, age matched controls (C n = 15). AS had a long history of AAS use (18 ± 2 yrs) and AS and C both had >19 years of resistance training. Participants underwent a resting electrocardiogram (ECG), from which, the QTc interval was calculated using the Bazett formula. The main outcome measure was significant differences in mean corrected QTc between groups. A secondary outcome was to calculate a QTc that best differentiated between C and AS. Results indicated that QTc was shorter in AS than in C (382.0 ± 21.01 ms versus 409 ± 18.77 ms for AS and C respectively p < 0.001). Chi squared analyses revealed a greater incidence of QTc < 380 ms in AS versus C p < 0.01, specificity 93% sensitivity 60%). In conclusion these results supports previous findings that AAS use causes a reduction in QTc, however, the specificity and sensitivity in our sample is lower than reported previously and precludes use as a screening tool.

Rapid normalization of vitamin D levels: a meta-analysis

BACKGROUND

Vitamin D deficiency may represent a modifiable risk factor to improve outcome in severe illness. The efficacy of high-dose regimens in rapid normalization of vitamin D levels is uncertain.

METHODS

We conducted a systematic review of pediatric clinical trials administering high-dose vitamin D to evaluate 25-hydroxyvitamin D (25[OH]D) response and characteristics associated with final 25(OH)D levels by using Medline, Embase, and the Cochrane Central Register of Controlled Trials, including reference lists of systematic reviews and eligible publications. Uncontrolled and controlled trials reporting 25(OH)D levels after high-dose (≥1000 IU) ergocalciferol or cholecalciferol were selected. Two reviewers independently extracted and verified predefined data fields.

RESULTS

We identified 88 eligible full-text articles. Two of 6 studies that administered daily doses approximating the Institute of Medicine's Tolerable Upper Intake Level (1000-4000 IU) to vitamin D-deficient populations achieved group 25(OH)D levels >75 nmol/L within 1 month. Nine of 10 studies evaluating loading therapy (>50 000 IU) achieved group 25(OH)D levels >75 nmol/L. In meta-regression, baseline 25(OH)D, regimen type, dose, age, and time factors were associated with final 25(OH)D levels. Adverse event analysis identified increased hypercalcemia risk with doses >400 000 IU, but no increased hypercalcemia or hypercalciuria with loading doses <400 000 IU (or 10 000 IU/kg). Few studies in adolescents evaluated loading dose regimens >300 000 IU.

CONCLUSIONS

Rapid normalization of vitamin D levels is best achieved by using loading therapy that considers disease status, baseline 25(OH)D, and age (or weight). Loading doses >300 000 IU should be avoided until trials are conducted to better evaluate risk and benefit.

Vitamin D supplementation and risk of toxicity in pediatrics: a review of current literature

CONTEXT

Although vitamin D toxicity is rare in children, increased use of vitamin D formulations, re-examination of optimal vitamin D levels, and use of higher doses lend potential for an increased incidence of vitamin D toxicity.

EVIDENCE ACQUISITION

A PubMed search was conducted through May 2013 for cases of vitamin D intoxication and vitamin D trials in pediatrics. Safety data were collected and reviewed.

EVIDENCE SYNTHESIS

A small number of pediatric studies tested vitamin D doses at or above the currently recommended upper tolerable intake. In children and adolescents, vitamin D excess was rare and usually asymptomatic. Recent cases of intoxication relate to errors in manufacturing, formulation, or prescription; involve high total intake in the range of 240,000 to 4,500,000 IU; and present with severe hypercalcemia, hypercalciuria, or nephrocalcinosis. However, mild hypercalcemia and hypervitaminosis using currently recommended doses have been reported in infants with rickets.

CONCLUSIONS

Although rare, cases of vitamin D intoxication that present with dramatic life-threatening symptoms still occur in children. Moreover, recent studies in infants raise a potential need for monitoring vitamin D levels when doses at or above the currently recommended upper range are used. Further studies are needed to clarify these findings. The Drugs and Therapeutics Committee of the Pediatric Endocrine Society suggests obtaining serum 25-hydroxyvitamin D levels in infants and children who receive long-term vitamin D supplementation at or above the upper level intake that is currently recommended.

Migrant and minority family members in the intensive care unit. A review of the literature

Statistics show that people with migrant and minority background as patients are significant in numbers in the intensive care unit. This also puts family members in the perspective of nursing because family members are an inherent part of the intensive care unit. Family-centered care is perhaps most applicable to vulnerable populations like migrant family in the intensive care unit to meet family member's needs. But very little is known about the situation of migrant and minority family members in the intensive care unit. The aim of the study was to explore the state of the science regarding family-centered care in the intensive care unit of patients with migration background in general and with a possible focus on major migrant populations in Austria-Former Yugoslavian und Turkish origin. A literature review investigated research articles that contained information on migrant and minority family members in the intensive care unit. Key points in the relevant articles were identified and categorized into themes with an explanation of findings at the end. Seventeen articles fulfilled the inclusion criteria. No article was found regarding groups of major migrant population groups in Austria. The included articles uncovered five predominant themes: importance of cultural norms, communication, family dynamics, universal caring, and nursing/provider deficit in culturally competent care. In order to provide adequate nursing care a more cohesive body of information on more specific geographic and cultural populations is recommended. Because of the complete lack of research regarding migrant families of Former Yugoslavian and Turkish origin into Austria, an exploration of this population is recommended.

Vitamin D deficiency in surgical congenital heart disease: prevalence and relevance

Vitamin D is a pleiotropic hormone important for the proper functioning of multiple organ systems. An emerging body of adult and pediatric critical care literature strongly suggests that vitamin D deficiency contributes to secondary organ pathophysiology, prolongs ICU stay, and worsens outcome in critically ill populations. Recent clinical studies suggest that a significant number of children with congenital heart disease (CHD) have post-operative vitamin D deficiency which appears to be associated with greater cardiovascular dysfunction. Altogether the cumulative body of literature suggests that peri-operative optimization of vitamin D status has the potential to speed recovery and/or improve outcome. This review describes the epidemiological and basic science research linking vitamin D deficiency to post-operative organ dysfunction. Furthermore, the available supplementation approaches are reviewed in the context of prevention of post-operative vitamin D deficiency and avoidance of toxicity in the majority of CHD patients. Finally, knowledge gaps regarding vitamin D supplementation are identified and the next stages for research are outlined.

Hypophosphatasia in a child with widened anterior fontanelle: lessons learned from late diagnosis and incorrect treatment

Hypophosphatasia is characterized by deficiency of serum alkaline phosphatase with defective bone and teeth mineralization. We report on an 11-month-old boy who developed a complex clinical picture characterized by bulging anterior fontanelle, growth failure, nephrocalcinosis and impaired bone mineralization during high-dose calcium and vitamin D supplementation. This therapy had been started 5 months earlier for a presumed diagnosis of nutritional rickets established on the grounds of isolated widened anterior fontanelle. However, laboratory investigations revealed reduced alkaline phosphatase levels associated with hypercalcemia, hypercalciuria, low PTH and normal 25-hydroxy vitamin D levels. Genetic testing detected a compound heterozygote for the novel mutation (c.262G>A) and the described mutation (c.920C>T) in the ALPL gene.

CONCLUSION

  High calcium and vitamin D supplementation should not be started in the presence of isolated signs of nutritional rickets without assessing calcium-phosphate metabolism. In fact, in rare bone-mineralizing disorders, this combined therapy might induce severe clinical complications.

Vitamin d toxicity in adults: a case series from an area with endemic hypovitaminosis d

Vitamin D deficiency state is endemic to the Kashmir valley of the Indian subcontinent. Physicians often treat patients with high doses of vitamin D for various ailments and on occasion the prescribed doses far exceed the requirements of the patients. Ten cases of hypercalcemia due to vitamin D intoxication are presented with features of vomiting, polyuria, polydipsia, encephalopathy and renal dysfunction. All the patients had demonstrable hypercalcemia and vitamin D levels were high in nine of the 10 cases. The patients had received high doses of vitamin D and no other cause of hypercalcemia was identified. Treatment of hypercalcemia resulted in clinical recovery in nine cases. We conclude that hypervitaminosis D must be considered in the differential diagnosis of patients with hypercalcemia in endemically vitamin D deficient areas. A careful history and appropriate biochemical investigation will unravel the diagnosis in most of the cases.

Collection of biological samples in forensic toxicology

Forensic toxicology is the study and practice of the application of toxicology to the purposes of the law. The relevance of any finding is determined, in the first instance, by the nature and integrity of the specimen(s) submitted for analysis. This means that there are several specific challenges to select and collect specimens for ante-mortem and post-mortem toxicology investigation. Post-mortem specimens may be numerous and can endow some special difficulties compared to clinical specimens, namely those resulting from autolytic and putrefactive changes. Storage stability is also an important issue to be considered during the pre-analytic phase, since its consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample. The knowledge on degradation mechanisms and methods to increase storage stability may enable the forensic toxicologist to circumvent possible difficulties. Therefore, advantages and limitations of specimen preservation procedures are thoroughfully discussed in this review. Presently, harmonized protocols for sampling in suspected intoxications would have obvious utility. In the present article an overview is given on sampling procedures for routinely collected specimens as well as on alternative specimens that may provide additional information on the route and timing of exposure to a specific xenobiotic. Last, but not least, a discussion on possible bias that can influence the interpretation of toxicological results is provided. This comprehensive review article is intented as a significant help for forensic toxicologists to accomplish their frequently overwhelming mission.

Vitamin D intoxication presenting as acute renal failure

A 70 year-old male presented with acute renal failure and mental obtundation. On examination, he was found to have hypercalcemia and on further questioning, it was found that it was secondary to injections of a slow-release vitamin D preparation. Although total body exposure is sufficient for vitamin D synthesis, increased vitamin D deficiency secondary to poor exposure to sunlight is observed in some parts of the world. We report here a case of vitamin D intoxication from the Kashmir valley where vitamin D deficiency is 100% in the general population that is confined indoors.

Breastfeeding does not protect against urinary tract infection in the first 3 months of life, but vitamin D supplementation increases the risk by 76%

Our goal was to determine if breastfeeding provides any protection against urinary tract infection (UTI) and if vitamin D supplementation imposes any additional risks for UTI in infants < 3 months of age. In this study, 40% of the children who had urine cultures were breastfed, and 18.7% of the children were exclusively breastfed. Twenty percent of all of the urine cultures tested positive, and this number was greater in females (22.5%) than in males (18.1%, P < .05). There was no significant difference between the rates of positive urine cultures in exclusively breastfed (22% vs 21%, nonsignificant [NS]) formula-fed infants. The relative risk of UTI with breastfeeding versus formula feeding was 1.03 (0.58-1.82), and any breastfeeding versus no breastfeeding was 0.92 (0.58-1.45). Vitamin D supplementation increased the UTI risk, with a relative risk of 1.76 (1.07-2.91, P < .05). However, only formula-fed infants showed an increased risk of UTI after vitamin D supplementation.

Vitamin D: current status and perspectives

The role of vitamin D in maintaining bone health has been known for decades. Recently, however, the discovery that many tissues expressed the vitamin D receptor and were able to transform the 25-OH vitamin D into its most active metabolite, 1,25-(OH)

Clin Chem Lab Med 2009;47:120–7.