| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
BRIEF REPORT |
Institute of Health Sciences, Faculty of Earth and Life Sciences, Vrije University (M.B.S., R.M.v.D., M.V., J.C.S.), 1081 HV Amsterdam, The Netherlands; and Institute for Research in Extramural Medicine (M.B.S., R.M.v.D., M.V., D.J.H.D., J.M.D., L.M.B., J.C.S., P.L.) and Department of Endocrinology (P.L.), Vrije University Medical Center, 1081 BT Amsterdam, The Netherlands
Address all correspondence and requests for reprints to: Dr. Marieke Snijder, Institute of Health Sciences, Faculty of Earth and Life Sciences, Vrije University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands. E-mail: marieke.snijder{at}falw.vu.nl.
 |
Abstract |
|---|
 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Methods: Subjects were participants of the Longitudinal Aging Study Amsterdam and were aged 65 yr and older. In 453 participants, serum 25-OH-D and PTH were determined, and body mass index, waist circumference, waist to hip ratio, sum of skin folds, and total body fat percentage by dual energy x-ray absorptiometry were measured.
Results: After adjustment for potential confounders, higher body mass index, waist circumference, and sum of skin folds were statistically significantly associated with lower 25-OH-D (standardized ß values were –0.136, –0.137, and –0.140, respectively; all P < 0.05) and with higher PTH (0.166, 0.113, and 0.114, respectively; all P < 0.05). Total body fat percentage was more strongly associated with 25-OH-D and PTH (–0.261 and 0.287, respectively; both P < 0.001) compared with anthropometric measures. Total body fat percentage remained associated with 25-OH-D after adjustment for PTH, and with PTH after adjustment for 25-OH-D.
Conclusion: Precisely measured total body fat is inversely associated with 25-OH-D levels and is positively associated with PTH levels. The associations were weaker if anthropometric measures were used, indicating a specific role of adipose tissue. Regardless of the possible underlying mechanisms, it may be relevant to take adiposity into account when assessing vitamin D requirements.
|
Introduction |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Evidence is increasing that the vitamin D endocrine system is related to obesity. Obesity has been found to be associated with lower levels of serum 25-hydroxyvitamin D (25-OH-D) (3, 4, 5, 6, 7, 8, 9, 10, 11) and higher levels of serum PTH (3, 8, 9, 12, 13). Underlying causes that have been suggested are less sun exposure in obese subjects due to limited mobility or clothing habits and a higher storage of vitamin D in adipose tissue (4, 11). However, overweight may also be the consequence of poor vitamin D status. Vitamin D is an important determinant of serum PTH levels, and increased PTH promotes calcium influx into the adipocytes. In these cells, intracellular calcium enhances lipogenesis, and therefore, PTH excess may promote weight gain (14, 15).
The relation between body fat content and serum 25-OH-D or PTH has usually been investigated in relatively small (case-control) studies (3, 4, 5, 7, 8, 9, 11). Furthermore, not many studies used direct measures of body fatness. The aim of the present study was to assess the association of adiposity with serum 25-OH-D and PTH levels in a large population-based study including older men and women.
|
Subjects and Methods |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
The Longitudinal Aging Study Amsterdam is an ongoing cohort study of the predictors and consequences of changes in autonomy and well-being in an aging population in The Netherlands. The sampling and data collection procedures have been described in detail previously (16). Briefly, a random sample of older men and women (aged 55–85 yr), stratified by age, sex, urbanization, and expected 5-yr mortality, was drawn from the population registers of 11 municipalities in areas in the west, northeast, and south of The Netherlands. In total, 3107 subjects participated in the baseline examination (1992/1993).
In 1995/1996, a second examination took place; participants were then aged 65 yr and older. After an interview at home, participants were invited for a medical interview at one of the research centers, where blood samples were obtained. Respondents living in the west (n = 685) were also invited for a whole body dual energy x-ray absorptiometry (DXA) scan, which was obtained for 518 respondents. The study sample for the present study included subjects in whom a DXA scan was performed and serum 25-OH-D and PTH levels were available (n = 514). Subjects with missing anthropometric information (n = 61) were excluded. Therefore, our final study sample consisted of 453 subjects who were predominantly Caucasian (99%). Informed consent was obtained from all respondents. The study was approved by the medical ethics committee of the Vrije University Medical Center.
Measurements
Blood samples were obtained and centrifuged in the morning. Subjects were allowed to have tea and toast, but no dairy products. The serum samples were stored at –70 C. Serum PTH was measured by an immunoradiometric assay (Incstar Corp., Stillwater, MN), and serum 25-OH-D was determined according to a competitive binding protein assay (Nichols Diagnostics, San Juan Capistrano, CA). The interassay coefficients of variation were 12 and 10%, respectively. The analyses were carried out at the Endocrine Laboratory of the Vrije University Medical Center.
The assessments of body mass index (BMI; kilograms per meter squared), waist circumference (centimeters), and waist to hip circumference ratio (WHR) have been described previously (17). The thicknesses of skin folds (millimeters) at the triceps, biceps, suprailiac, and subscapular were measured in triplicate, and the sum of the mean thickness of each skin fold was used in the analyses.
Total body fat (kilograms) was measured by whole body DXA (software version V5.67A, QDR 2000, Hologic, Inc., Waltham, MA). The system software first determines bone mineral content and soft tissue compartments. Then soft tissue is further separated into fat and fat-free soft tissue masses. The total body fat percentage (percentage) was calculated as (total body fat/total body weight) x 100.
Because vitamin D status is partly dependent on sunlight exposure, we adjusted for the season of data collection. Because mild renal impairment could affect PTH and 25-OH-D homeostasis, we also adjusted for serum creatinine. The level of physical activity (minutes per day) was estimated by a validated interview-administered questionnaire for older subjects (18). Smoking status was classified as smoker or nonsmoker (cigarettes, tobacco, cigar, and pipe), and alcohol use was classified as light, moderate, excessive, or very excessive, based on the alcohol consumption index of Garretsen (19).
Statistical analyses
All analyses were performed using SPSS for Windows (version 11.0.1, SPSS, Inc., Chicago, IL). Multiple linear regression analyses were performed to study the associations between body composition variables (independent variables) and serum 25-OH-D or PTH levels (dependent variables). Because the distribution of serum PTH was skewed, we used the logarithmic transformation. We adjusted for potential confounders by adding them to the regression models. Effect modification by sex was evaluated by stratified analyses and tested by adding product terms of body composition variables x sex to the regression models. To facilitate direct comparisons of the strengths of the associations, the results of the regression models are reported as standardized ß values. A standardized ß of 0.2 indicates that if the independent variable increases by 1 SD, the dependent variable increases by 0.2 SD.
|
Results |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
shows the characteristics of the study participants according to sex-specific quartiles of total body fat percentage. Total body fat was inversely associated with serum 25-OH-D and positively with serum PTH levels in both sexes (all P < 0.05). In 8.0% of the men and 14.4% of the women, the serum 25-OH-D level was less than 10 ng/ml (25 nmol/liter; deficient status), and 44.7% of the men and 56.1% of the women had serum 25-OH-D levels below 20 ng/ml (50 nmol/liter; insufficient status). Anthropometric measures were also inversely related to 25-OH-D, but this crude association was only statistically significant for BMI and waist circumference in women (P < 0.05). BMI, waist circumference, and sum of skin folds were statistically significantly and positively associated with serum PTH in women only (all P < 0.05).
|
, model 1). The associations of DXA total body fat (either in kilograms or as a percentage) with serum 25-OH-D and PTH levels were stronger than the associations of the anthropometric measures and were statistically significant for both men and women (Table 2 and Fig. 1).
|
|
).
Additional adjustment of the associations for serum creatinine, alcohol intake, or physical activity level (total activity or outdoor activities only) did not appreciably change the associations (data not shown). After adjustment for smoking, the associations became stronger (change of >10%); therefore, we presented the associations after adjustment for smoking. The Pearson correlation coefficient between serum 25-OH-D and ln-PTH was –0.30. Additional adjustment for PTH considerably weakened the associations between measures of body fatness and 25-OH-D, and additional adjustment for 25-OH-D considerably weakened the associations between measures of body fatness and PTH (Table 2, model 2). Most associations with DXA-measured total body fat, however, remained statistically significant.
When we distinguished trunk fat from leg fat and added them simultaneously to the regression models as two separate independent variables, leg fat was a strong determinant of 25-OH-D, whereas trunk fat was not significantly associated with 25-OH-D [standardized ß value, –0.161 (P = 0.017) and –0.054 (P = 0.341), respectively]. In contrast, trunk fat was a strong determinant of PTH levels, whereas leg fat was not significantly associated with PTH [standardized ß value, 0.155 (P = 0.013) and 0.055 (P = 0.457), respectively].
|
Discussion |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
In the 1980s, small case-control studies showed that serum 25-OH-D levels were lower in obese subjects compared with nonobese individuals (3, 4, 20), and serum PTH levels were higher (3), which was confirmed in more recent studies (5, 9, 11). In observational studies, similar associations of BMI with 25-OH-D or PTH were shown (7, 8, 12, 13), but these were not always statistically significant (6, 10, 21). In our sample we found statistically significant associations between BMI and 25-OH-D and between BMI and PTH levels. However, the associations of these hormones with total body fat percentage by DXA were even stronger, which was also found in younger women (mean age, 47 yr) (10). These results indicate that it is adiposity, and not simply body weight or BMI, that is associated with serum 25-OH-D and PTH concentrations. Previous studies have probably underestimated the associations by using anthropometric measures.
In reports from the 1970s (22, 23), it was suggested that the association between serum 25-OH-D and obesity could be explained by an increased storage of 25-OH-D in adipose tissue in obese subjects. Rosenstreich et al. (22) supplemented rats with radiolabeled vitamin D, and adipose tissue was found to be the major storage site. Mawer et al. (23) found similar results in human tissues after injection of radioactive cholecalciferol. In a more recent study by Wortsman et al. (11), the capacity of the skin to produce vitamin D was not altered in obesity. However, the increase in serum vitamin D3 after sun exposure was 57% less in obese compared with nonobese subjects. The increase in serum vitamin D3 after oral supplementation was similar in obese and nonobese subjects. This supports the hypothesis of a decreased release of endogenously produced vitamin D into the circulation due to more storage in sc fat in obese subjects (11). The fact that in our study leg fat was more strongly related to 25-OH-D levels compared with trunk fat supports the idea that endogenously produced vitamin D is particularly stored in the sc fat depot (11).
Recently, evidence has been accumulating that obesity can also be the consequence of a low vitamin D status. Increased PTH levels, of which serum 25-OH-D is an important determinant, promote calcium influx into the adipocytes. In these cells intracellular calcium enhances lipogenesis; therefore, PTH excess may promote weight gain (14, 15). The fact that PTH was also associated with adiposity after adjustment for 25-OH-D could suggest that PTH, also independently of 25-OH-D, contributes to the development of adiposity. The observation that a higher dietary intake of calcium, which is related to lower PTH levels, is related to lower body weight (24) and less weight gain (25) also fits the hypothesis of high PTH levels as a cause of obesity. Subjects with primary hyperparathyroidism, who have increased PTH levels, were also markedly heavier than age-matched controls (26, 27). In addition, calcium supplementation, which also decreases PTH levels, resulted in a greater weight loss compared with placebo treatment (25, 28). These intervention studies suggest a modest, but causal, relation between serum PTH and weight change. Serum 25-OH-D is an important determinant of PTH levels, and interventions have shown that supplementation with 
-calcidol resulted in modest, but significant, weight loss (29, 30). In our study, however, the 25-OH-D level was also related to adiposity independently of PTH levels.
In conclusion, in a large population-based study, including both men and women, we found that total body fat percentage measured by DXA is strongly associated with serum 25-OH-D and PTH levels, independently of age, sex, season, or smoking. The associations were weaker if anthropometric measures were used, indicating a specific role of adipose tissue. Long-term longitudinal studies with repeated measures of vitamin D and PTH should be performed to explore the direction of effects underlying our observations. Considering the possible role of vitamin D and PTH in the development of cancer, muscle weakness, insulin resistance, diabetes, and cardiovascular disease (31, 32, 33), it may be relevant to take adiposity into account when assessing vitamin D requirements.
|
Footnotes |
|---|
First Published Online April 26, 2005
Abbreviations: BMI, Body mass index; DXA, dual energy x-ray absorptiometry; 25-OH-D, 25-hydroxyvitamin D; WHR, waist to hip ratio.
Received February 1, 2005.
Accepted April 18, 2005.
|
References |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
-calcidol) in middle-aged men with impaired glucose tolerance. Effects on insulin secretion and sensitivity, glucose tolerance and blood pressure. Diabetes Res 11:141–147[Medline]
-hydroxycholecalciferol in middle-aged men with impaired glucose tolerance: a prospective randomized double-blind study. Acta Med Scand 222:361–367[Medline]
This article has been cited by other articles:
 |
|
 |
|
  A. Zittermann, S. Frisch, H. K Berthold, C. Gotting, J. Kuhn, K. Kleesiek, P. Stehle, H. Koertke, and R. Koerfer Vitamin D supplementation enhances the beneficial effects of weight loss on cardiovascular disease risk markers Am. J. Clinical Nutrition, May 1, 2009; 89(5): 1321 - 1327. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Orwoll, C. M. Nielson, L. M. Marshall, L. Lambert, K. F. Holton, A. R. Hoffman, E. Barrett-Connor, J. M. Shikany, T. Dam, J. A. Cauley, et al. Vitamin D Deficiency in Older Men J. Clin. Endocrinol. Metab., April 1, 2009; 94(4): 1214 - 1222. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M Smith, K. K Gardner, J. Locke, and S. R Zwart Vitamin D supplementation during Antarctic winter Am. J. Clinical Nutrition, April 1, 2009; 89(4): 1092 - 1098. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. L. Nelson, J. M. Blum, B. W. Hollis, C. Rosen, and S. S. Sullivan Supplements of 20 {micro}g/d Cholecalciferol Optimized Serum 25-Hydroxyvitamin D Concentrations in 80% of Premenopausal Women in Winter J. Nutr., March 1, 2009; 139(3): 540 - 546. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Liu, J. B. Meigs, A. G. Pittas, N. M. McKeown, C. D. Economos, S. L. Booth, and P. F. Jacques Plasma 25-Hydroxyvitamin D Is Associated with Markers of the Insulin Resistant Phenotype in Nondiabetic Adults J. Nutr., February 1, 2009; 139(2): 329 - 334. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Muntner, T. M. Jones, A. D. Hyre, M. L. Melamed, A. Alper, P. Raggi, and M. B. Leonard Association of Serum Intact Parathyroid Hormone with Lower Estimated Glomerular Filtration Rate Clin. J. Am. Soc. Nephrol., January 1, 2009; 4(1): 186 - 194. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M Sneve, Y Figenschau, and R Jorde Supplementation with cholecalciferol does not result in weight reduction in overweight and obese subjects Eur. J. Endocrinol., December 1, 2008; 159(6): 675 - 684. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. E. Christensen, P. H Nissen, P. Vestergaard, L. Heickendorff, L. Rejnmark, K. Brixen, and L. Mosekilde Plasma 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and parathyroid hormone in familial hypocalciuric hypercalcemia and primary hyperparathyroidism Eur. J. Endocrinol., December 1, 2008; 159(6): 719 - 727. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D.-H. Manicourt and J.-P. Devogelaer Urban Tropospheric Ozone Increases the Prevalence of Vitamin D Deficiency among Belgian Postmenopausal Women with Outdoor Activities during Summer J. Clin. Endocrinol. Metab., October 1, 2008; 93(10): 3893 - 3899. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. M. Ochs-Balcom, M. S. Cicek, C. L. Thompson, T. C. Tucker, R. C. Elston, S. J.Plummer, G. Casey, and L. Li Association of vitamin D receptor gene variants, adiposity and colon cancer Carcinogenesis, September 1, 2008; 29(9): 1788 - 1793. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. A. Cauley, A. Z. LaCroix, L. Wu, M. Horwitz, M. E. Danielson, D. C. Bauer, J. S. Lee, R. D. Jackson, J. A. Robbins, C. Wu, et al. Serum 25-Hydroxyvitamin D Concentrations and Risk for Hip Fractures Ann Intern Med, August 19, 2008; 149(4): 242 - 250. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Misra, D. Pacaud, A. Petryk, P. F. Collett-Solberg, M. Kappy, and on behalf of the Drug and Therapeutics Committee o Vitamin D Deficiency in Children and Its Management: Review of Current Knowledge and Recommendations Pediatrics, August 1, 2008; 122(2): 398 - 417. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. J. G. Hoogendijk, P. Lips, M. G. Dik, D. J. H. Deeg, A. T. F. Beekman, and B. W. J. H. Penninx Depression Is Associated With Decreased 25-Hydroxyvitamin D and Increased Parathyroid Hormone Levels in Older Adults Arch Gen Psychiatry, May 1, 2008; 65(5): 508 - 512. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. M. Bodnar, J. M. Catov, J. M. Roberts, and H. N. Simhan Prepregnancy Obesity Predicts Poor Vitamin D Status in Mothers and Their Neonates J. Nutr., November 1, 2007; 137(11): 2437 - 2442. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A H Zargar, S Ahmad, S R Masoodi, A I Wani, M I Bashir, B A Laway, and Z A Shah Vitamin D status in apparently healthy adults in Kashmir Valley of Indian subcontinent Postgrad. Med. J., November 1, 2007; 83(985): 713 - 716. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J Bolland, A. B Grey, R. W Ames, B. H Mason, A. M Horne, G. D Gamble, and I. R Reid The effects of seasonal variation of 25-hydroxyvitamin D and fat mass on a diagnosis of vitamin D sufficiency Am. J. Clinical Nutrition, October 1, 2007; 86(4): 959 - 964. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. P. Kovesdy, S. Ahmadzadeh, J. E. Anderson, and K. Kalantar-Zadeh Obesity Is Associated with Secondary Hyperparathyroidism in Men with Moderate and Severe Chronic Kidney Disease Clin. J. Am. Soc. Nephrol., September 1, 2007; 2(5): 1024 - 1029. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Reinehr, G. de Sousa, U. Alexy, M Kersting, and W. Andler Vitamin D status and parathyroid hormone in obese children before and after weight loss Eur. J. Endocrinol., August 1, 2007; 157(2): 225 - 232. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. S. Harris and B. Dawson-Hughes Reduced Sun Exposure Does Not Explain the Inverse Association of 25-Hydroxyvitamin D with Percent Body Fat in Older Adults J. Clin. Endocrinol. Metab., August 1, 2007; 92(8): 3155 - 3157. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. L Weng, J. Shults, M. B Leonard, V. A Stallings, and B. S Zemel Risk factors for low serum 25-hydroxyvitamin D concentrations in otherwise healthy children and adolescents Am. J. Clinical Nutrition, July 1, 2007; 86(1): 150 - 158. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. P. Reis, D. von Muhlen, D. Kritz-Silverstein, D. L. Wingard, and E. Barrett-Connor Vitamin D, Parathyroid Hormone Levels, and the Prevalence of Metabolic Syndrome in Community-Dwelling Older Adults Diabetes Care, June 1, 2007; 30(6): 1549 - 1555. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Caan, M. Neuhouser, A. Aragaki, C. B. Lewis, R. Jackson, M. S. LeBoff, K. L. Margolis, L. Powell, G. Uwaifo, E. Whitlock, et al. Calcium Plus Vitamin D Supplementation and the Risk of Postmenopausal Weight Gain Arch Intern Med, May 14, 2007; 167(9): 893 - 902. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. S Riedt, Y. Schlussel, N. von Thun, H. Ambia-Sobhan, T. Stahl, M P. Field, R. M Sherrell, and S. A Shapses Premenopausal overweight women do not lose bone during moderate weight loss with adequate or higher calcium intake Am. J. Clinical Nutrition, April 1, 2007; 85(4): 972 - 980. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. S. Tworoger, I-M. Lee, J. E. Buring, B. Rosner, B. W. Hollis, and S. E. Hankinson Plasma 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D and Risk of Incident Ovarian Cancer Cancer Epidemiol. Biomarkers Prev., April 1, 2007; 16(4): 783 - 788. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. M van Dam, M. B Snijder, J. M Dekker, C. D. Stehouwer, L. M Bouter, R. J Heine, and P. Lips Potentially modifiable determinants of vitamin D status in an older population in the Netherlands: the Hoorn Study Am. J. Clinical Nutrition, March 1, 2007; 85(3): 755 - 761. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. N Hathcock, A. Shao, R. Vieth, and R. Heaney Risk assessment for vitamin D Am. J. Clinical Nutrition, January 1, 2007; 85(1): 6 - 18. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Hypponen and C. Power Vitamin D Status and Glucose Homeostasis in the 1958 British Birth Cohort: The role of obesity Diabetes Care, October 1, 2006; 29(10): 2244 - 2246. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Visser, D. J. Deeg, M. T. Puts, J. C Seidell, and P. Lips Low serum concentrations of 25-hydroxyvitamin D in older persons and the risk of nursing home admission. Am. J. Clinical Nutrition, September 1, 2006; 84(3): 616 - 622. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B Moosgaard, P Vestergaard, L Heickendorff, F Melsen, P Christiansen, and L Mosekilde Plasma 25-hydroxyvitamin D and not 1,25-dihydroxyvitamin D is associated with parathyroid adenoma secretion in primary hyperparathyroidism: a cross-sectional study. Eur. J. Endocrinol., August 1, 2006; 155(2): 237 - 244. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Kong and Y. C. Li Molecular mechanism of 1,25-dihydroxyvitamin D3 inhibition of adipogenesis in 3T3-L1 cells Am J Physiol Endocrinol Metab, May 1, 2006; 290(5): E916 - E924. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.-T. Gau, S. Clay, and W. Carlsen Parathyroid hormone, vitamin D, and calcium intake. JAMA, April 19, 2006; 295(15): 1769 - 1769. [Full Text] [PDF]
|
|
|
|
|
|
L. Steingrimsdottir, O. Gunnarsson, O. S. Indridason, L. Franzson, and G. Sigurdsson Parathyroid Hormone, Vitamin D, and Calcium Intake--Reply JAMA, April 19, 2006; 295(15): 1769 - 1770. [Full Text] [PDF]
|
|
|
|
 |
|
 M. F. Holick High Prevalence of Vitamin D Inadequacy and Implications for Health Mayo Clin. Proc., March 1, 2006; 81(3): 353 - 373. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
