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Marcela Moraes Mendes Department of Nutrition, Faculty of Health Sciences, University of Brasília, Distrito Federal, Brazil
Department of Nutrition, Institute of Life Sciences, Federal University of Juiz de Fora, Governador Valadares, Minas Gerais, Brazil
Department of Nutrition, Faculty of Health and Medical Sciences, University of Surrey, University of Surrey, Guildford, UK

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Patricia Borges Botelho Department of Nutrition, Faculty of Health Sciences, University of Brasília, Distrito Federal, Brazil

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Helena Ribeiro Department of Environmental Health, Faculty of Public Health, University of São Paulo, São Paulo, Brazil

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Vitamin D enhances calcium absorption and bone mineralisation, promotes maintenance of muscle function, and is crucial for musculoskeletal health. Low vitamin D status triggers secondary hyperparathyroidism, increases bone loss, and leads to muscle weakness. The primary physiologic function of vitamin D and its metabolites is maintaining calcium homeostasis for metabolic functioning, signal transduction, and neuromuscular activity. A considerable amount of human evidence supports the well-recognised contribution of adequate serum 25-hydroxyvitamin D concentrations for bone homeostasis maintenance and prevention and treatment strategies for osteoporosis when combined with adequate calcium intake. This paper aimed to review the literature published, mainly in the last 20 years, on the effect of vitamin D and its supplementation for musculoskeletal health in order to identify the aspects that remain unclear or controversial and therefore require further investigation and debate. There is a clear need for consistent data to establish realistic and meaningful recommendations of vitamin D status that consider different population groups and locations. Moreover, there is still a lack of consensus on thresholds for vitamin D deficiency and optimal status as well as toxicity, optimal intake of vitamin D, vitamin D supplement alone as a strategy to prevent fractures and falls, recommended sun exposure at different latitudes and for different skin pigmentations, and the extra skeletal effects of vitamin D.

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Stefan Pilz Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Armin Zittermann Clinic for Thoracic and Cardiovascular Surgery, Herz- und Diabeteszentrum NRW, Ruhr University Bochum, Bad Oeynhausen, Germany

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Christian Trummer Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Verena Theiler-Schwetz Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Elisabeth Lerchbaum Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Martin H Keppel University Institute for Medical and Chemical Laboratory Diagnostics, Paracelsus Medical University, Salzburg, Austria

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Martin R Grübler Department of Cardiology, Swiss Cardiovascular Center Bern, Bern University Hospital, University of Bern, Bern, Switzerland

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Winfried März Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria
Medical Clinic V (Nephrology, Hypertensiology, Rheumatology, Endocrinology, Diabetology), Medical Faculty Mannheim, Ruperto-Carola University of Heidelberg, Heidelberg, Germany
Synlab Medical Center of Human Genetics Mannheim, Mannheim, Germany

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Marlene Pandis Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria

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Vitamin D testing and treatment is a subject of controversial scientific discussions, and it is challenging to navigate through the expanding vitamin D literature with heterogeneous and partially opposed opinions and recommendations. In this narrative review, we aim to provide an update on vitamin D guidelines and the current evidence on the role of vitamin D for human health with its subsequent implications for patient care and public health issues. Vitamin D is critical for bone and mineral metabolism, and it is established that vitamin D deficiency can cause rickets and osteomalacia. While many guidelines recommend target serum 25-hydroxyvitamin D (25[OH]D) concentrations of ≥50 nmol/L (20 ng/mL), the minimum consensus in the scientific community is that serum 25(OH)D concentrations below 25–30 nmol/L (10–12 ng/mL) must be prevented and treated. Using this latter threshold of serum 25(OH)D concentrations, it has been documented that there is a high worldwide prevalence of vitamin D deficiency that may require public health actions such as vitamin D food fortification. On the other hand, there is also reason for concern that an exploding rate of vitamin D testing and supplementation increases costs and might potentially be harmful. In the scientific debate on vitamin D, we should consider that nutrient trials differ from drug trials and that apart from the opposed positions regarding indications for vitamin D treatment we still have to better characterize the precise role of vitamin D for human health.

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Glenville Jones Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, Ontario, Canada

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Vitamin D has many physiological functions including upregulation of intestinal calcium and phosphate absorption, mobilization of bone resorption, renal reabsorption of calcium as well as actions on a variety of pleiotropic functions. It is believed that many of the hormonal effects of vitamin D involve a 1,25-dihydroxyvitamin D3-vitamin D receptor-mediated transcriptional mechanism involving binding to the cellular chromatin and regulating hundreds of genes in many tissues. This comprehensive historical review provides a unique perspective of the many steps of the discovery of vitamin D and its deficiency disease, rickets, stretching from 1650 until the present. The overview is divided into four distinct historical phases which cover the major developments in the field and in the process highlighting the: (a) first recognition of rickets or vitamin D deficiency; (b) discovery of the nutritional factor, vitamin D and its chemical structure; (c) elucidation of vitamin D metabolites including the hormonal form, 1,25-dihydroxyvitamin D3; (d) delineation of the vitamin D cellular machinery, functions and vitamin D-related diseases which focused on understanding the mechanism of action of vitamin D in its many target cells.

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Johanna Öberg Tromso Endocrine Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway, Tromso, Norway

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Rolf Jorde Tromso Endocrine Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway, Tromso, Norway

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Yngve Figenschau Tromso Endocrine Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway, Tromso, Norway
Diagnostic Clinic, University Hospital of North Norway, Tromso, Norway

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Per Medbøe Thorsby Hormone Laboratory, Department of Medical Biochemistry and Biochemical Endocrinology and Metabolism Research Group, Oslo University Hospital, Aker, Oslo, Norway

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Sandra Rinne Dahl Hormone Laboratory, Department of Medical Biochemistry and Biochemical Endocrinology and Metabolism Research Group, Oslo University Hospital, Aker, Oslo, Norway

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Anne Winther Division of Neurosciences, Orthopedics and Rehabilitation Services, University Hospital of North Norway, Tromso, Norway

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Guri Grimnes Tromso Endocrine Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway, Tromso, Norway
Division of Internal Medicine, University Hospital of North Norway, Tromso, Norway

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Objective

Combined hormonal contraceptive (CHC) use has been associated with higher total 25-hydroxyvitamin D (25(OH)D) levels. Here, we investigate the relation between CHC use and vitamin D metabolism to elucidate its clinical interpretation.

Methods

The cross-sectional Fit Futures 1 included 1038 adolescents. Here, a subgroup of 182 girls with available 25(OH)D, 1,25-dihydroxyvitamin D (1,25(OH)2D), 24,25-dihydroxyvitamin D (24,25(OH)2D), vitamin D-binding protein (DBP) and measured free 25(OH)D levels, in addition to parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23), was investigated. Vitamin D metabolites were compared between girls using (CHC+) and not using CHC (CHC−). Further, the predictability of CHC on 25(OH)D levels was assessed in a multiple regression model including lifestyle factors. The ratios 1,25(OH)2D/25(OH)D and 24,25(OH)2D/25(OH)D (vitamin D metabolite ratio (VMR)) in relation to 25(OH)D were presented in scatterplots.

Results

CHC+ (n  = 64; 35% of the girls) had higher 25(OH)D levels (mean ± s.d., 60.3 ± 22.2) nmol/L) than CHC- (n  = 118; 41.8 ± 19.3 nmol/L), P -values <0.01. The differences in 25(OH)D levels between CHC+ and CHC− were attenuated but remained significant after the adjustment of lifestyle factors. CHC+ also had higher levels of 1,25(OH)2D, 24,25(OH)2D, DBP and calcium than CHC−, whereas 1,25(OH)2D/25(OH)D, PTH, FGF23 and albumin were significantly lower. Free 25(OH)D and VMR did not statistically differ, and both ratios appeared similar in relation to 25(OH)D, irrespective of CHC status.

Conclusion

This confirms a clinical impact of CHC on vitamin D levels in adolescents. Our observations are likely due to an increased DBP-concentration, whereas the free 25(OH)D appears unaltered.

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Gabriella Oliveira Lima Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Alex Luiz Menezes da Silva Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Julianne Elba Cunha Azevedo Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Chirlene Pinheiro Nascimento Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Luana Rodrigues Vieira Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Akira Otake Hamoy Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Luan Oliveira Ferreira Laboratory of Experimental Neuropathology, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Verônica Regina Lobato Oliveira Bahia Multidisciplinary Laboratory of Animal Morphology, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Nilton Akio Muto Amazon Bioactive Compounds Valorization Center, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Dielly Catrina Favacho Lopes Laboratory of Experimental Neuropathology, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Moisés Hamoy Laboratory of Pharmacology and Toxicology of Natural Products, Institute of Biological Sciences, Federal University of Pará, Belém, Pará, Brazil

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Low plasma levels of vitamin D causes bone mineral change that can precipitate osteopenia and osteoporosis and could aggravate autoimmune diseases, hypertension and diabetes. The demand for vitamin D supplementation becomes necessary; however, the consumption of vitamin D is not without risks, which its toxicity could have potentially serious consequences related to hypervitaminosis D, such as hypercalcemia and cerebral alterations. Thus, the present study describes the electroencephalographic changes caused by supraphysiological doses of vitamin D in the brain electrical dynamics and the electrocardiographic changes. After 4 days of treatment with vitamin D at a dose of 25,000 IU/kg, the serum calcium levels found were increased in comparison with the control group. The electrocorticogram analysis found a reduction in wave activity in the delta, theta, alpha and beta frequency bands. For ECG was observed changes with shortened QT follow-up, which could be related to serum calcium concentration. This study presented important evidence about the cerebral and cardiac alterations caused by high doses of vitamin D, indicating valuable parameters in the screening and decision-making process for diagnosing patients with symptoms suggestive of intoxication.

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Natércia Neves Marques de Queiroz University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Franciane Trindade Cunha de Melo University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Fabrício de Souza Resende University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Luísa Corrêa Janaú University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Norberto Jorge Kzan de Souza Neto University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Manuela Nascimento de Lemos University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Ana Carolina Lobato Virgolino University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Maria Clara Neres Iunes de Oliveira University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Angélica Leite de Alcântara University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Lorena Vilhena de Moraes University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Tiago Franco David University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Wanderson Maia da Silva University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Scarlatt Souza Reis University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Márcia Costa dos Santos University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Ana Carolina Contente Braga de Souza University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Pedro Paulo Freire Piani University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Neyla Arroyo Lara Mourão University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Karem Mileo Felício University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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João Felício Abrahão Neto University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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João Soares Felício University Hospital João de Barros Barreto, Federal University of Pará, Endocrinology Division, Belem, Pará, Brazil

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Objective:

Investigate the prevalence of vitamin D deficiency in an equatorial population through a large-sample study.

Methods:

Cross-sectional study with 30,224 healthy individuals from the North Region, in Brazil (Amazônia – state of Pará), who had 25-hydroxy-vitamin D (25(OH)D) and intact parathyroid hormone (PTH) serum levels measured by immunoassay method. Those with history of acute or chronic diseases were excluded. Abnormal levels of calcium, creatinine, glycemia and albumin were also exclusion criteria.

Results:

25(OH)D levels were 29.1 ± 8.2 ng/mL and values <12.7 ng/mL were equal to < −2 s.d. below average. Hypovitaminosis D was present in 10% of subjects according to the Institute of Medicine (values <20 ng/mL) and in 59%, in consonance with Endocrine Society (values 20–30 ng/mL as insufficiency and <20 ng/mL as deficiency) criteria. Individuals were divided according to four age brackets: children, adolescents, adults and elderly, and their 25(OH)D levels were: 33 ± 9; 28.5 ± 7.4; 28.3 ± 7.7; 29.3 ± 8.5 ng/mL, respectively. All groups differed in 25(OH)D, except adolescents vs adults. Regression model showed BMI, sex, living zone (urban or rural) and age as independent variables to 25(OH)D levels. Comparing subjects with vitamin D deficiency (<20 ng/mL) to those with vitamin D insufficiency (20–30 ng/mL), a difference between PTH levels in these two groups was observed (95.9 ± 24.7 pg/mL vs 44.2 ± 64.5 pg/mL; P < 0.01). Additionally, the most accurate predictive vitamin D level for subclinical hyperparathyroidism in ROC curve was 26 ng/mL.

Conclusion:

Our equatorial population showed low prevalence of vitamin D hypovitaminosis ranging with age bracket. The insufficient category by Endocrine Society was corroborated by our PTH data.

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A Chinoy Royal Manchester Children’s Hospital, Manchester, UK

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M Skae Royal Manchester Children’s Hospital, Manchester, UK

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A Babiker King Abdullah Specialized Children’s Hospital, Riyadh, Saudi Arabia

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D Kendall Royal Preston Hospital, Preston, UK

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M Z Mughal Royal Manchester Children’s Hospital, Manchester, UK

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R Padidela Royal Manchester Children’s Hospital, Manchester, UK

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Background

Hypoparathyroidism is characterised by hypocalcaemia, and standard management is with an active vitamin D analogue and adequate oral calcium intake (dietary and/or supplements). Little is described in the literature about the impact of intercurrent illnesses on calcium homeostasis in children with hypoparathyroidism.

Methods

We describe three children with hypoparathyroidism in whom intercurrent illnesses led to hypocalcaemia and escalation of treatment with alfacalcidol (1-hydroxycholecalciferol) and calcium supplements.

Results

Three infants managed with standard treatment for hypoparathyroidism (two with homozygous mutations in GCMB2 gene and one with Sanjad-Sakati syndrome) developed symptomatic hypocalcaemia (two infants developed seizures) following respiratory or gastrointestinal illnesses. Substantial increases in alfacalcidol doses (up to three times their pre-illness doses) and calcium supplementation were required to achieve acceptable serum calcium concentrations. However, following resolution of illness, these children developed an increase in serum calcium and hypercalciuria, necessitating rapid reduction to pre-illness dosages of alfacalcidol and oral calcium supplementation.

Conclusion

Intercurrent illness may precipitate symptomatic hypocalcaemia in children with hypoparathyroidism, necessitating increase in dosages of alfacalcidol and calcium supplements. Close monitoring is required on resolution of the intercurrent illness, with timely reduction of dosages of active analogues of vitamin D and calcium supplements to prevent hypercalcaemia, hypercalciuria and nephrocalcinosis.

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Shu-Meng Hu Department of Nephrology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Yang-Juan Bai Department of Laboratory Medicine/Research Centre of Clinical Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Ya-Mei Li Department of Laboratory Medicine/Research Centre of Clinical Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Ye Tao Department of Nephrology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Xian-Ding Wang Department of Urology/Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Tao Lin Department of Urology/Institute of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Lan-Lan Wang Department of Laboratory Medicine/Research Centre of Clinical Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Yun-Ying Shi Department of Nephrology, West China Hospital, Sichuan University, Chengdu, Sichuan, China

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Introduction

Tertiary hyperparathyroidism (THPT) and vitamin D deficiency are commonly seen in kidney transplant recipients, which may result in persistently elevated fibroblast growth factor 23 (FGF23) level after transplantation and decreased graft survival. The aim of this study is to evaluate the effect of vitamin D supplementation on THPT, FGF23-alpha Klotho (KLA) axis and cardiovascular complications after transplantation.

Materials and methods

Two hundred nine kidney transplant recipients were included and further divided into treated and untreated groups depending on whether they received vitamin D supplementation. We tracked the state of THPT, bone metabolism and FGF23–KLA axis within 12 months posttransplant and explored the predictors and risk factors for intact FGF23 levels, KLA levels, THPT and cardiovascular complications in recipients.

Results

Vitamin D supplementation significantly improved FGF23 resistance, THPT and high bone turnover status, preserved better graft function and prevented coronary calcification in the treated group compared to the untreated group at month 12. The absence of vitamin D supplementation was an independent risk factor for THPT and a predictor for intact FGF23 and KLA levels at month 12. Age and vitamin D deficiency were independent risk factors for coronary calcification in recipients at month 12.

Conclusion

Vitamin D supplementation effectively improved THPT, FGF23 resistance and bone metabolism, preserved graft function and prevented coronary calcification after transplantation.

Open access
Ranganathan R Rao Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Harpal S Randeva Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Sailesh Sankaranarayanan Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Murthy Narashima Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Matthias Möhlig Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Hisham Mehanna Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Martin O Weickert Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
Warwickshire Institute for the Study of Diabetes, Warwick Medical School, Department of Endocrinology, Institute of Head and Neck Studies and Education (InHANSE), Endocrinology and Metabolism, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK

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Introduction/background

Vitamin D deficiency further increases circulating parathyroid hormone (PTH) levels in patients with primary hyperparathyroidism (pHPT), with potential detrimental effects on bone mass.

Methods

This was an observational clinical study in consecutive conservatively treated postmenopausal women (n=40) with pHPT and coexistent 25-hydroxyvitamin D deficiency (25OHD ≤50 nmol/l (≤20 ng/ml)). Patients who showed an increase in serum 25OHD above the threshold of vitamin D deficiency (>50 nmol/l; n=28) using treatment with various commonly prescribed vitamin D preparations were, for the purposes of statistical analyses, allocated to the treatment group. Patients who were retrospectively identified as having received no treatment with vitamin D and/or remained vitamin D deficient were considered as non-responders/controls (n=12). Adjusted calcium (adjCa), PTH and 25OHD concentrations were monitored in all subjects up to 54 months (mean observation period of 18±2 months).

Results

Prolonged increased vitamin D intake, regardless of the source (serum 25OHD, increase from 32.2±1.7 nmol/l at baseline to 136.4±11.6 nmol/l, P<0.0001), significantly reduced serum PTH (13.3±1.1 vs 10.5±1.0 pmol/l, P=0.0001), with no adverse effects on adjCa levels (2.60±0.03 vs 2.60±0.02 mmol/l, P=0.77) and renal function tests (P>0.73). In contrast, serum PTH remained unchanged (15.8±2.6 vs 16.3±1.9 pmol/l, P=0.64) in patients who remained vitamin D deficient, with a significant difference between groups in changes of PTH (P=0.0003). Intrapartial correlation analyses showed an independent negative correlation of changes in 25OHD with PTH levels (r ic=−0.41, P=0.014).

Conclusions

Prolonged treatment with vitamin D in various commonly prescribed preparations appeared to be safe and significantly reduced PTH levels by 21%.

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Sharon A Huish University Hospitals of Coventry and Warwickshire NHS Trust, Coventry, UK
The University of Warwick, Coventry, UK
Royal Devon and Exeter NHS Foundation Trust, Exeter, UK

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Carl Jenkinson The University of Birmingham, Birmingham, UK

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Janet A Dunn The University of Warwick, Coventry, UK

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David J Meredith Royal Devon and Exeter NHS Foundation Trust, Exeter, UK

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Rosemary Bland The University of Warwick, Coventry, UK

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Martin Hewison The University of Birmingham, Birmingham, UK

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Low serum 1,25-dihydroxyvitamin D (1,25(OH)2D) in end-stage renal disease (ESRD) is considered a consequence of elevated fibroblast growth factor 23 (FGF23) and concomitant reduced activity of renal 1α-hydroxylase (CYP27B1). Current ESRD treatment strategies to increase serum calcium and suppress secondary hyperparathyroidism involve supplementation with vitamin D analogues that circumvent 1α-hydroxylase. This overlooks the potential importance of 25-hydroxyvitamin D (25(OH)D) deficiency as a contributor to low serum 1,25(OH)2D. We investigated the effects of vitamin D (cholecalciferol) supplementation (40,000 IU for 12 weeks and maintenance dose of 20,000 IU fortnightly), on multiple serum vitamin D metabolites (25(OH)D, 1,25(OH)2D3 and 24,25(OH)2D3) in 55 haemodialysis patients. Baseline and 12 month data were compared using related-samples Wilcoxon signed rank test. All patients remained on active vitamin D analogues as part of routine ESRD care. 1,25(OH)2D3 levels were low at baseline (normal range: 60–120 pmol/L). Cholecalciferol supplementation normalised both serum 25(OH)D and 1,25(OH)2D3. Median serum 25(OH)D increased from 35.1 nmol/L (IQR: 23.0–47.5 nmol/L) to 119.9 nmol/L (IQR: 99.5–143.3 nmol/L) (P < 0.001). Median serum 1,25(OH)2D3 and 24,25(OH)2D3 increased from 48.3 pmol/L (IQR: 35.9–57.9 pmol/L) and 3.8 nmol/L (IQR: 2.3–6.0 nmol/L) to 96.2 pmol/L (IQR: 77.1–130.6 pmol/L) and 12.3 nmol/L (IQR: 9–16.4 nmol/L), respectively (P < 0.001). A non-significant reduction in daily active vitamin D analogue dose occurred, 0.94 µmcg at baseline to 0.77 µmcg at 12 months (P = 0.73). The ability to synthesise 1,25(OH)2D3 in ESRD is maintained but is substrate dependent, and serum 25(OH)D was a limiting factor at baseline. Therefore, 1,25(OH)2D3 deficiency in ESRD is partly a consequence of 25(OH)D deficiency, rather than solely due to reduced 1α-hydroxylase activity as suggested by current treatment strategies.

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