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Posts Tagged ‘Parathyroid hormone’


Larry, H. Bernstein, MD, FCAP, Author and Curator
Http://pharmaceuticalintelligence.com/2013-12-4/larryhbern/Vitamin_D_-_Binding_Protein_and_Vitamin_D_Status

Vitamin D–Binding Protein and Vitamin D Status of Black Americans and White Americans

CE Powe, MK Evans, J Wenger, AB Zonderman, AH Berg, M Nalls, H Tamez, et al.
N Engl J Med 21 Nov,2013; 369:1991-2000
http://dx.doi.org/10.1056/NEJMoa1306357

Summary

BACKGROUND

Low levels of total 25-hydroxyvitamin D are common among black Americans. Vitamin D–binding protein has not been considered in the assessment of vitamin D deficiency.

METHODS

In the Healthy Aging in Neighborhoods of Diversity across the Life Span cohort of blacks and whites (2085 participants), we measured
  • levels of total 25-hydroxyvitamin D,
  • vitamin D–binding protein, and
  • parathyroid hormone as well as
  • bone mineral density (BMD).

We genotyped study participants for two common polymorphisms in the vitamin D–binding protein gene (rs7041 and rs4588). We estimated levels of bioavailable 25-hydroxyvitamin D in homozygous participants. 

RESULTS

Mean (±SE) levels of both total 25-hydroxyvitamin D and vitamin D–binding protein were lower in blacks than in whites (total 25-hydroxyvitamin D, 15.6±0.2 ng per milliliter vs. 25.8±0.4 ng per milliliter, P<0.001; vitamin D–binding protein, 168±3 μg per milliliter vs. 337±5 μg per milliliter, P<0.001).
  • Genetic polymorphisms independently appeared to explain 79.4% and 9.9% of the variation in levels of vitamin D–binding protein and total 25-hydroxyvitamin D, respectively.
  • BMD was higher in blacks than in whites (1.05±0.01 g per square centimeter vs. 0.94±0.01 g per square centimeter, P<0.001).
  • Levels of parathyroid hormone increased with decreasing levels of total or bioavailable 25-hydroxyvitamin D (P<0.001 for both relationships),
    • yet within each quintile of parathyroid hormone concentration, blacks had significantly lower levels of total 25-hydroxyvitamin D than whites.

Among homozygous participants, blacks and whites had similar levels of bioavailable 25-hydroxyvitamin D overall (2.9±0.1 ng per milliliter and 3.1±0.1 ng per milliliter, respectively; P=0.71) and

  • within quintiles of parathyroid hormone concentration.

CONCLUSIONS

Community-dwelling black Americans, as compared with whites, had low levels of total 25-hydroxyvitamin D and vitamin D–binding protein,
  • resulting in similar concentrations of estimated bioavailable 25-hydroxyvitamin D.

Racial differences in the prevalence of common genetic polymorphisms provide a likely explanation for this observation. (Funded by the National Institute on Aging and others.)

 

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Reported by: Dr. Venkat S. Karra, Ph.D.

Recent study by Margareta Ring, et.al., indicates that Arterial Structure and Function in Mild Primary Hyperparathyroidism Is Not Directly Related to Parathyroid Hormone, Calcium, or Vitamin D.

They found normal arterial function, despite high PTH and Ca as well as low vitamin D levels, in patients with mild PHPT without cardiovascular risk factors.

English: Main complications of persistent high...

The cardiovascular risk associated with low vitamin D and/or high PTH and Ca levels may be explained by their coupling to blood pressure and other risk factors rather than direct effects on the arterial structure, author said. Research findings support the importance of adequate blood pressure control in PHPT if PTX is not performed, but do not indicate vascular abnormalities motivating extended follow-up after PTX.

 

 

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