scholarly journals In Healthy Adults, Biological Activity of Vitamin D, as Assessed by Serum PTH, Is Largely Independent of DBP Concentrations

2014 ◽  
Vol 29 (2) ◽  
pp. 494-499 ◽  
Author(s):  
Zari Dastani ◽  
Claudie Berger ◽  
Lisa Langsetmo ◽  
Lei Fu ◽  
Betty YL Wong ◽  
...  
Keyword(s):  
Vitamin D ◽  
Biological Activity ◽  
Healthy Adults ◽  
Serum Pth

Comparison of total, free and bioavailable 25-OH vitamin D determinations to evaluate its biological activity in healthy adults: the LabOscat study

2017 ◽  
Vol 28 (8) ◽  
pp. 2457-2464 ◽  
Author(s):  
P. Peris ◽  
◽  
X. Filella ◽  
A. Monegal ◽  
N. Guañabens ◽  
...  
Keyword(s):  
Vitamin D ◽  
Biological Activity ◽  
Healthy Adults ◽  
25 Oh Vitamin D

scholarly journals Biological activity of 24,24-difluoro-25-hydroxyvitamin D3. Effect of blocking of 24-hydroxylation on the functions of vitamin D.

1979 ◽  
Vol 254 (15) ◽  
pp. 7163-7167
Author(s):  
Y Tanaka ◽  
H F DeLuca ◽  
Y Kobayashi ◽  
T Taguchi ◽  
N Ikekawa ◽  
...  
Keyword(s):  
Vitamin D ◽  
Biological Activity

The Effects of Diphosphonate on the Metabolism and Biological Activity of Vitamin D

1972 ◽  
Vol 42 (4) ◽  
pp. 16P-16P ◽  
Author(s):  
L. F. Hill ◽  
E. B. Mawer ◽  
G. A. Lumb ◽  
S. W. Stanbury
Keyword(s):  
Vitamin D ◽  
Biological Activity

scholarly journals Epimers of Vitamin D: A Review

2020 ◽  
Vol 21 (2) ◽  
pp. 470 ◽  
Author(s):  
Bashar Al-Zohily ◽  
Asma Al-Menhali ◽  
Salah Gariballa ◽  
Afrozul Haq ◽  
Iltaf Shah
Keyword(s):  
Vitamin D ◽  
Biological Activity ◽  
Hydroxyl Group ◽  
Vitamin D Metabolites ◽  
Dihydroxyvitamin D3 ◽  
In Vivo Models ◽  
Vitamin D Receptors ◽  
Potential Factors

In this review, we discuss the sources, formation, metabolism, function, biological activity, and potency of C3-epimers (epimers of vitamin D). We also determine the role of epimerase in vitamin D-binding protein (DBP) and vitamin D receptors (VDR) according to different subcellular localizations. The importance of C3 epimerization and the metabolic pathway of vitamin D at the hydroxyl group have recently been recognized. Here, the hydroxyl group at the C3 position is orientated differently from the alpha to beta orientation in space. However, the details of this epimerization pathway are not yet clearly understood. Even the gene encoding for the enzyme involved in epimerization has not yet been identified. Many published research articles have illustrated the biological activity of C3 epimeric metabolites using an in vitro model, but the studies on in vivo models are substantially inadequate. The metabolic stability of 3-epi-1α,25(OH)2D3 has been demonstrated to be higher than its primary metabolites. 3-epi-1 alpha, 25 dihydroxyvitamin D3 (3-epi-1α,25(OH)2D3) is thought to have fewer calcemic effects than non-epimeric forms of vitamin D. Some researchers have observed a larger proportion of total vitamin D as C3-epimers in infants than in adults. Insufficient levels of vitamin D were found in mothers and their newborns when the epimers were not included in the measurement of vitamin D. Oral supplementation of vitamin D has also been found to potentially cause increased production of epimers in mice but not humans. Moreover, routine vitamin D blood tests for healthy adults will not be significantly affected by epimeric interference using LC–MS/MS assays. Recent genetic models also show that the genetic determinants and the potential factors of C3-epimers differ from those of non-C3-epimers.Most commercial immunoassays techniques can lead to inaccurate vitamin D results due to epimeric interference, especially in infants and pregnant women. It is also known that the LC–MS/MS technique can chromatographically separate epimeric and isobaric interference and detect vitamin D metabolites sensitively and accurately. Unfortunately, many labs around the world do not take into account the interference caused by epimers. In this review, various methods and techniques for the analysis of C3-epimers are also discussed. The authors believe that C3-epimers may have an important role to play in clinical research, and further research is warranted.

scholarly journals Effects of Age and Serum 25-OH-Vitamin D on Serum Parathyroid Hormone Levels

2012 ◽  
Vol 97 (11) ◽  
pp. 3989-3995 ◽  
Author(s):  
A. Valcour ◽  
F. Blocki ◽  
D. M. Hawkins ◽  
Sudhaker D. Rao
Keyword(s):  
Vitamin D ◽  
Calcium Absorption ◽  
Small Sample Size ◽  
International Workshop ◽  
Large Population ◽  
Small Sample ◽  
Reference Laboratory ◽  
Population Database ◽  
Age Related ◽  
Serum Pth

Context: Several studies define optimal serum 25-hydroxyvitamin D (25-OHD) levels based on serum PTH level reaching an asymptote. However, results differ widely, ranging from 25-OHD levels of 12–44 ng/ml: many studies are constrained by small sample size. Objective: The objective of the study was to determine the relationship between serum PTH and 25-OHD levels and age in a very large reference laboratory database. Design: This was a detailed cross-sectional analysis of 312,962 paired serum PTH and 25-OHD levels measured from July 2010 to June 2011. Results: Median PTH levels and the proportion of patients (PTH > 65 pg/ml), from 63 successive 25-OHD frequency classes of 5000 patients, provide smooth, exceptionally well-fitted curves (R2 = 0.994 and R2 = 0.995, respectively) without discernible inflection points or asymptotes but with striking age dependencies. Serum 25-OHD was below the recent Institute of Medicine sufficiency guidance of 20 ng/ml in 27% (85,000) of the subjects. More importantly, 40 and 51% of subjects (serum 25-OHD <20 and 10 ng/ml, respectively) had biochemical hyperparathyroidism (PTH > 65 pg/ml). Conclusions: This analysis, despite inevitable inherent limitations, introduces several clinical implications. First, median 25-OHD-dependent PTH levels revealed no threshold above which increasing 25-OHD fails to further suppress PTH. Second, the large number of subjects with 25-OHD deficiency and hyperparathyroidism reinforces the Third International Workshop on Asymptomatic Primary Hyper parathyroidism's recommendations to test for, and replete, vitamin D depletion before considering parathyroidectomy. Third, strong age dependency of the PTH-25-OHD relationship likely reflects the composite effects of age-related decline in calcium absorption and renal function. Finally, this unselected large population database study could guide clinical management of patients based on an age-dependent, PTH-25-OHD continuum.

Effect of Phenobarbitone Treatment on Vitamin D Metabolism in Mammals

1974 ◽  
Vol 46 (4) ◽  
pp. 433-448 ◽  
Author(s):  
J. Silver ◽  
G. Neale ◽  
G. R. Thompson
Keyword(s):  
Vitamin D ◽  
Biological Activity ◽  
Silicic Acid ◽  
Vitamin D3 ◽  
Water Soluble ◽  
Prolonged Treatment ◽  
Vitamin D Metabolism ◽  
Silicic Acid Chromatography ◽  
Polar Metabolites ◽  
25 Hydroxycholecalciferol

1. The metabolism of radioactive cholecalciferol was studied in control and phenobarbitone-treated rats and pigs. 2. Treatment with phenobarbitone enhanced the appearance in plasma of 25-hydroxycholecalciferol (peak IV on silicic acid chromatography), and of more-polar metabolites (peak V), but not of the most-polar metabolites (peak VI). Peak IV had the chromatographic properties of authentic 25-hydroxycholecalciferol (25-HCC) and had biological activity. 3. There was no effect on the appearance of peaks V and VI in plasma after an injection of radioactive 25-HCC. 4. Treatment with phenobarbitone enhanced the excretion of metabolites of radioactive vitamin D3 in bile. These metabolites were largely water-soluble conjugates of peaks IV, V and VI, which included glucuronides. Peak IV in bile was not identical with 25-HCC. 5. Prolonged treatment with phenobarbitone depleted the tissue radioactivity of rats given radioactive vitamin D3.

scholarly journals Craniotabes in Normal Newborns: The Earliest Sign of Subclinical Vitamin D Deficiency

2008 ◽  
Vol 93 (5) ◽  
pp. 1784-1788 ◽  
Author(s):  
Junko Yorifuji ◽  
Tohru Yorifuji ◽  
Kenji Tachibana ◽  
Shizuyo Nagai ◽  
Masahiko Kawai ◽  
...  
Keyword(s):  
Vitamin D ◽  
Vitamin D Deficiency ◽  
Urinary Calcium ◽  
University Hospital ◽  
X Rays ◽  
Intact Pth ◽  
Calcium Phosphorus ◽  
Serum Pth ◽  
Normal Neonates ◽  
Breast Fed

Abstract Context: Craniotabes in otherwise normal neonates has been regarded as physiological and left untreated. Objective: Our objective was to investigate the role of vitamin D deficiency in the development of craniotabes in normal neonates. Design and Setting: Newborn screening of craniotabes was conducted at the single largest obstetrical facility in Kyoto, Japan. Follow-up study at 1 month was conducted at Kyoto University Hospital. Subjects: A total of 1120 consecutive normal Japanese neonates born in May, 2006, through April, 2007, were included in the study. Main Outcome Measures: The incidence of craniotabes was scored each month. Neonates with craniotabes were followed up at 1 month with measurements of serum calcium, phosphorus, alkaline phosphatase (ALP), intact PTH, 25-OH vitamin D (25-OHD), urinary calcium, phosphorus, creatinine, and hand x-rays. Results: Craniotabes was present in 246 (22.0%) neonates, and the incidence had obvious seasonal variations, highest in April-May and lowest in November. At 1 month, infants with craniotabes had significantly higher serum ALP compared with normal neonates; 6.9% of them had elevated intact PTH over 60 pg/ml, and 37.3% had 25-OHD less than 10 ng/ml. When separately analyzed according to the method of feeding, 56.9% of breast-fed infants showed 25-OHD less than 10 ng/ml, whereas none of formula/mixed-fed infants did, and breast-fed infants had significantly higher serum PTH and ALP compared with formula/mixed-fed infants. Summary: These results suggest that craniotabes in normal neonates is associated with vitamin D deficiency in utero, and the deficiency persists at 1 month in many of them, especially when breast-fed.

Synthesis and Biological Activity of Vitamin D Conjugates

Vitamin D ◽  
1984 ◽  
pp. 523-538
Author(s):  
S. Nagubandi ◽  
R. Kumar
Keyword(s):  
Vitamin D ◽  
Biological Activity
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