title: Older people in China and the United Kingdom differ in the relationships among parathyroid hormone, vitamin D, and bone mineral status.
abstract: To explore whether there are ethnic differences in relationships among parathyroid hormone (PTH), vitamin D, and bone mineral status, 352 healthy volunteers, 60-83 years old, were studied in Shenyang, Peoples' Republic of China (108 men, 110 women), and in Cambridge, UK (67 men, 67 women), in late winter. Early morning fasting blood and 2-h fasting urine were analyzed for 25-hydroxyvitamin D (25OH-D), PTH, and free deoxypyridinoline (DPD). Hip bone mineral status was measured using dual-energy X-ray absorptiometry (Lunar). There were significant differences (P < 0.001) in plasma 25OH-D and PTH concentrations between Shenyang and Cambridge [25OH-D nmol/L: Shenyang = 29.0 (SD 12.7), Cambridge = 35.7 (12.9)]; PTH ng/L: Shenyang = 34.3 (13.4), Cambridge = 25.2 (11.0)]. PTH was negatively related to 25OH-D in both populations. The relationship was exponential, best described by an inverse log-log equation with no break point (P < 0.001), indicating that the exponential curve did not tend toward a low plateau. PTH was higher for a given 25OH-D and decreased less with increasing 25OH-D in Shenyang than in Cambridge (country-ln25OH-D interaction, P = 0.0005). After adjusting for bone area, weight, height, age, and sex, hip bone mineral content (BMC) was significantly related to PTH concentration in Cambridge but not in Shenyang [femoral neck coefficient: Cambridge = -0.064 (SE 0.027), P = 0.02; Shenyang = -0.027 (0.028), P = 0.3; trochanter: Cambridge = -0.116 (0.034), P = 0.001; Shenyang = -0.019 (0.027), P = 0.5]. There was a significant country-lnPTH interaction at the trochanter (P = 0.02), but not at the femoral neck (P = 0.7). A weak positive association between BMC at the femoral neck and 25OH-D concentration was found in Cambridge [coefficient: 0.054 (0.028), P = 0.05] but not in Shenyang (coefficient: -0.013, P = 0.5; country-ln25OH-D interaction, P = 0.07). Urinary DPD concentration was also positively related to plasma PTH concentration in Cambridge subjects only [coefficient: 0.2 (0.08), P = 0.02]. These data suggest that although PTH increases when 25OH-D decreases, and Chinese people have a higher PTH for a given 25OH-D, older Chinese adults may be more resistant than Britons to the effects of PTH on bone.
authors.affiliation: Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK. Liya.Yan@mrc-hnr.cam.ac.uk
authors.forename: L
authors.initials: L
authors.lastname: Yan
authors.forename: B
authors.initials: B
authors.lastname: Zhou
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: S
authors.initials: S
authors.lastname: D'Ath
authors.forename: A
authors.initials: A
authors.lastname: Laidlaw
authors.forename: M A
authors.initials: MA
authors.lastname: Laskey
authors.forename: A
authors.initials: A
authors.lastname: Prentice
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000596:Amino Acids / Q000652:urine; D015519:Bone Density / Q000502:physiology*; D002112:Calcifediol / Q000097:blood*; D002681:China; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000209:etiology; D010281:Parathyroid Hormone / Q000097:blood*; D012621:Seasons; D006113:United Kingdom
chemical_list: D000596:Amino Acids; D010281:Parathyroid Hormone; C036020:deoxypyridinoline; D002112:Calcifediol