We aimed to describe the vitamin D status of young women living in two Chinese cities in the spring -Beijing in the north (latitude 398 north) and Hong Kong (latitude 228 north) in the south. We also examined the relationship between serum 25-hydroxyvitamin D and parathyroid hormone (PTH) concentrations to determine a threshold for serum 25-hydroxyvitamin D above which there is no further suppression of PTH. Finally, we examined whether dietary Ca intake influences this relationship. Non-pregnant women aged 18-40 years (n 441) were recruited between February and June. Over 60 % of women in a recent survey in Hong Kong (n 547) indicated that they did not like going in the sun 10 .Vitamin D insufficiency increases blood parathyroid hormone (PTH) concentration. Chronically elevated PTH (secondary hyperparathyroidism) accelerates bone turnover and is thought to be the key mechanism of cortical bone loss related to vitamin D insufficiency 11 . PTH concentrations

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