title: Vitamin D, parathyroid hormone levels and bone mineral density in community-dwelling older women: the Rancho Bernardo Study.
abstract: Vitamin D (25(OH)D) increases the efficiency of intestinal calcium absorption. Low levels of serum calcium stimulate the secretion of parathyroid hormone (PTH), which maintains serum calcium levels at the expense of increased bone turnover, bone loss and increased risk of fractures. We studied the association between 25(OH)D and PTH levels, and their associations with bone mineral density (BMD), bone loss, and prevalence of hip fractures in 615 community-dwelling postmenopausal aged 50-97 years. Mean level of 25(OH)D and PTH were 102.0 nmol/l+/-35.0 nmol/l and 49.4 ng/l+/-23.2 nmol/l, respectively; 49% of women were current hormone therapy users. The overall prevalence of vitamin D insufficiency (25(OH)D<50 nmol/l) was 2%, and prevalence of high PTH levels (>65 ng/l) was 17.4%. In multiple linear regression analyses hip BMD was negatively and independently associated with PTH levels (p=0.04), and positively and independently associated with 25(OH)D levels (p=0.03). There were only 23 women (3.7%) who experienced a hip fracture. In age-adjusted analyses there were no significant differences of 25(OH)D and PTH levels by hip fracture status. Across the entire range of values, the overall correlation between 25(OH)D and PTH was moderate (r=-0.20). However, after the threshold vitamin D level of 120 nmol/l, all PTH values were below 65 ng/l. Further studies are necessary to identify the optimal vitamin D levels necessary to prevent secondary hyperparathyroidism.
authors.affiliation: Division of Epidemiology, Department of Family and Preventive Medicine, University of California, San Diego, La Jolla, CA 92093, USA. dvonmuhlen@ucsd.edu
authors.forename: Denise G
authors.initials: DG
authors.lastname: von Mühlen
authors.forename: Gail A
authors.initials: GA
authors.lastname: Greendale
authors.forename: Cedric F
authors.initials: CF
authors.lastname: Garland
authors.forename: Lori
authors.initials: L
authors.lastname: Wan
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Barrett-Connor
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology*; D002112:Calcifediol / Q000097:blood; D002136:Calcium, Dietary / Q000008:administration & dosage; D015331:Cohort Studies; D003404:Creatinine / Q000493:pharmacokinetics; D019587:Dietary Supplements; D005260:Female; D006620:Hip Fractures / Q000097:blood / Q000453:epidemiology / Q000503:physiopathology; D020249:Hormone Replacement Therapy; D006801:Humans; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000097:blood / Q000503:physiopathology; D010281:Parathyroid Hormone / Q000097:blood*; D015995:Prevalence; D012307:Risk Factors; D014807:Vitamin D / Q000008:administration & dosage / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology / Q000503:physiopathology
chemical_list: D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D014807:Vitamin D; D003404:Creatinine; D002112:Calcifediol