Article

Relationship between Vitamin D, Parathyroid Hormone, and Bone Health

Bone Metabolism Unit, Department of Medicine, Creighton University Medical Center, 601 North 30 Street, Suite 6718, Omaha, Nebraska 68131, USA.
The Journal of Clinical Endocrinology and Metabolism (Impact Factor: 6.31). 03/2011; 96(3):E436-46. DOI: 10.1210/jc.2010-1886
Source: PubMed

ABSTRACT There is a controversy regarding the definition of vitamin D insufficiency as it relates to bone health.
The objective of the study was to examine the evidence for a threshold value of serum 25-hydroxyvitamin D (25OHD) that defines vitamin D insufficiency as it relates to bone health.
This was a cross-sectional analysis of baseline data in 488 elderly Caucasian women, mean age 71 yr, combined with a literature review of 70 studies on the relationship of serum PTH to serum 25OHD.
The study was conducted in independent-living women in the midwest United States.
The relationship between serum 25OHD, serum PTH, and serum osteocalcin and 24-h urine N-telopeptides was evaluated.
Serum PTH was inversely correlated with serum 25OHD (r = -0.256, P < 0.0005), but no threshold as defined by suppression of serum PTH was found within the serum 25OHD range 6-60 ng/ml (15-150 nmol/liter). However, in contrast, there was a threshold for bone markers, serum osteocalcin and urine N-telopeptides, that increased only below a serum 25OHD of approximately 18 ng/ml (45 nmol/liter). Calcium absorption was not correlated with serum PTH and serum 25OHD, and no threshold was found. A literature review of 70 studies generally showed a threshold for serum PTH with increasing serum 25OHD, but there was no consistency in the threshold level of serum 25OHD that varied from 10 to 50 ng/ml (25-125 nmol/liter).
Vitamin D insufficiency should be defined as serum 25OHD less than 20 ng/ml (50 nmol/liter) as it relates to bone.

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