Changes in Biochemical Markers of Bone Turnover and in Calcaneal Ultrasonometric Parameters during Wintering in the Antarctic

This report describes the changes in ultrasound parameters of the right calcaneus and the blood and urinary biochemical data of 40 members of the 35th Japanese Antarctic Research Expedition during the winter period of their expedition in the Antarctic. The members consisted of two groups, the Syowa Station Group and the Travelers Group. Serum 25-hydroxyvitamin D [25(OH)D] in the Station Group showed seasonal changes, being lower in winter and higher in summer, while serum 1,25-dihydroxyvitamin D [1,25(OH)_2D] decreased gradually during their residence at the Syowa Station, and did not return to normal even after the end of winter. In the Syowa Station Group, both serum Ca and serum inorganized phosphate decreased gradually, showing statistically low values after the winter, while the serum parathyroid hormone (PTH) showed no significant changes during same period. As for bone forming markers, osteocalcin was significantly decreased during the winter whereas both serum tartrate procollagen type 1 carboxyterminal extension peptide (P1CP) and ALP increased in the Station Group. Bone resorbing markers, such as urinary pyridinoline, urinary deoxypyridinoline, and serum procollagen type 1 C-terminal propeptide (1CTP), showed a significant decrease. As for ultrasonometric parameters of the right calcaneus, no significant difference in the speed of sound (SOS), the broadband ultrasound attenuation (BUA) and the stiffness index (stiffness as calculated from the combined SOS and BUA values by a computer program provided by the manufacturer) was observed during the entire stay. The unique environment with its insufficient exposure to sunlight (Ultra violet light) and insufficient intake of Ca from food, was reputed to have reduced the bone remodeling in the Station Group. The present study showed no significant changes in the ultrasound parameters, probably due to a short stay of only one winter. In the Travelers Group, SOS on the spring and summer trips and stiffness on all three trips increased significantly after traveling; serum 25(OH)D showed seasonal changes similar to the Station Group, while other parameters of bone turnover showed no specific tendency. These results suggest that the high altitude (hypoxia, the Dome Fuji Station being located 3,800 m above sea level) and the daily riding of snow vehicles for lengthy times over a period of about three weeks on highly uneven snow surfaces are related to the changes in bone metabolism