Vitamin D status and parathyroid hormone relationship in adolescents and its association with bone health parameters: analysis of the Northern Ireland Young Heart's Project.
In girls, a plateau in parathyroid hormone (PTH) was observed at a 25-hydroxyvitamin D (25(OH)D) concentration of approximately 60 nmol/l. In boys, there was no plateau in PTH concentrations as 25(OH)D concentration increased. A 25(OH)D threshold of 60 nmol/l appears to have implications for bone health outcomes in both girls and boys.


BACKGROUND
Our objective was to investigate if there is a threshold 25(OH)D concentration where a plateau in PTH concentration is evident and to examine the impact of this relationship on bone mineral density (BMD) and bone turnover in a representative sample of adolescents.


METHODS
We conducted a cross-sectional analysis among 1,015 Northern Irish adolescents aged 12 and 15 years. Serum 25(OH)D, PTH, osteocalcin, type 1 collagen cross-linked C-telopeptide (CTx), and BMD of the nondominant forearm and heel were measured. Nonlinear regression analysis was used to model the association between 25(OH)D and PTH.


RESULTS
In girls, a plateau in PTH was observed at a 25(OH)D concentration of approximately 60 nmol/l (PTH = 47.146 + 370.314 x exp((-0.092 x 25(OH)D))) while no plateau in PTH was observed in boys (PTH = 42.144 + 56.366 x exp((-0.022 x 25(OH)D))). Subjects with 25(OH)D levels <60 nmol/l had significantly higher osteocalcin concentrations (P < 0.05) compared with those who had >or=60 nmol/l, while no significant (P > 0.05) differences were noted for CTx concentrations. In girls only, nondominant forearm BMD but not heel BMD was significantly higher (P = 0.046) in those with 25(OH)D concentrations >or= 60 nmol/l.


CONCLUSIONS
Serum 25(OH)D levels above 60 nmol/l in Northern Irish adolescent girls prevent an increase in serum PTH levels and maintaining 25(OH)D >60 nmol/l in both girls and boys may lead to improved bone health outcomes.
Department of Food and Nutritional Sciences, University College, Cork, Ireland. t.hill@ucc.ie
T R
TR
Hill
A A
AA
Cotter
S
S
Mitchell
C A
CA
Boreham
W
W
Dubitzky
L
L
Murray
J J
JJ
Strain
A
A
Flynn
P J
PJ
Robson
J M W
JM
Wallace
M
M
Kiely
K D
KD
Cashman
D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology*; D002648:Child; D024042:Collagen Type I / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood*; D010455:Peptides / Q000097:blood; D012737:Sex Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
D015415:Biomarkers; D024042:Collagen Type I; D010281:Parathyroid Hormone; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D014807:Vitamin D; C104450:25-hydroxyvitamin D