Skeletal and hormonal responses to sunlight deprivation in Antarctic expeditioners
Iuliano-Burns, S and Wang, XF and Ayton, J and Jones, G and Seeman, E, Skeletal and hormonal responses to sunlight deprivation in Antarctic expeditioners, Osteoporosis International, 20, (9) pp. 1523-1528. ISSN 0937-941X (2009) [Refereed Article]
Summary Serum 25(OH)D levels decline without sunlight
exposure. We studied 120 expeditioners to Antarctica to
determine the skeletal and hormonal responses to sunlight
deprivation. With emerging vitamin D insufficiency, serum
calcium decreased, PTH increased, and bone loss at the
proximal femur was observed. Baseline serum 25(OH)D
levels >100 nmol/L prevented vitamin D insufficiency.
Introduction Vitamin D stores deplete without adequate
sunlight exposure unless supplementation is provided. We
studied 120 healthy adults who spent a year in Antarctica as
a model for sunlight deprivation to define the timing and
magnitude of the skeletal and hormonal responses to
emerging vitamin D insufficiency.
Methods Fasting blood samples were assessed at baseline,
6 and 12 months for serum 25-hydroxyvitamin D
(25(OH)D), osteocalcin (OC), bone formation (P1NP)
and resorption (CTx), PTH and calcium. Lumbar spine
and proximal femur BMD was measured using DXA.
Differences over time were determined using repeated
measures ANOVA. Percent changes were expressed as
(âó value/(value A+value B)/2)ü~100. Relationships between
outcome measures were determined using Spearmanüfs
Results Vitamin D insufficiency (<50 nmol/L) was observed
in 85% of expeditioners by 6 months when serum calcium
decreased and PTH increased (p<0.01). By 12 months, OC
increased by 7.4ü}3.0% (p<0.05), and BMD decreased by
1.0ü}2.0% at the total proximal femur (p<0.05). For those
with vitamin D sufficiency at baseline (>50 nmol/L),
sunlight deprivation produced vitamin D insufficiency
within 4 months unless baseline values were >100 nmol/L.
Conclusion Supplementation may be necessary for expeditioners
with limited access to UV light.