Higher 25-hydroxyvitamin Research Articles

High serum 25-hydroxyvitamin D is associated with a low incidence of stress fractures

Low serum 25-hydroxyvitamin D [25(OH)D] concentrations are associated with hip fractures, but the dose-response relationship of serum 25(OH)D with risk of stress fractures in young women is unknown. This nested case-control study in a cohort of female Navy recruits was designed to determine whether those with low prediagnostic serum 25(OH)D concentrations had greater risk of stress fracture. Sera were drawn in 2002-2009 from 600 women who were diagnosed subsequently with stress fracture of the tibia or fibula and 600 matched controls who did not experience a stress fracture. The 25(OH)D concentration was measured using the DiaSorin radioimmunoassay method. Controls were individually matched to cases on race (white, black, or other), length of service (±30 days), and day blood was drawn (±2 days). There was approximately half the risk of stress fracture in the top compared with the bottom quintile of serum 25(OH)D concentration (odds ratio [OR] = 0.51, 95% CI 0.34-0.76, p ≤ 0.01). The range of serum 25(OH)D in the lowest quintile was 1.5 to 19.7 (mean 13.9) ng/mL, whereas in the highest it was 39.9 to 112 (mean 49.7) ng/mL. It is concluded that there was a monotonic inverse dose-response gradient between serum 25(OH)D and risk of stress fracture. There was double the risk of stress fractures of the tibia and fibula in women with serum 25(OH)D concentrations of less than 20 ng/mL compared to those with concentrations of 40 ng/mL or greater. A target for prevention of stress fractures would be a serum 25(OH)D concentration of 40 ng/mL or greater, achievable with 4000 IU/d of vitamin D(3) supplementation.

Glycemic changes after vitamin D supplementation in patients with type 1 diabetes mellitus and vitamin D deficiency

BACKGROUND:A prospective, nonblinded and nonrandomized controlled trial was conducted to test the hypothesis that vitamin D supplementation would improve glycemic control in patients with type 1 diabetes mellitus who have vitamin D deficiency.PATIENTS AND METHODS:Eighty patients with type 1 diabetes mellitus who had 25-hydroxyvitamin D levels less than 50 nmol/L were assigned to receive 4000 IU of vitamin D3. Calcium supplements were provided to ensure a total calcium intake of 1200 mg/d. Glycosylated hemoglobin and 25-hydroxyvitamin D levels were measured at baseline and at 12 weeks.RESULTS:There was a significant difference in mean (SD) glycosylated hemoglobin level (%) between the groups that achieved 25-hydroxyvitamin D levels of <35.4 nmol/L, 35.4-51 nmol/L and >51 nmol/L at 12 weeks (P=.02). There was a significant difference in glycosylated hemoglobin change from baseline between the groups that achieved 25-hydroxyvitamin D levels of <35.4 nmol/L, 35.4-51 nmol/L and >51 nmol/L at 12 weeks (P=.04). There was a significant difference in 25-hydroxyvitamin D level between the groups that achieved glycosylated hemoglobin levels of <7.8, 7.8-9.9 and >9.9 at 12 weeks (P=.001). Patients were more likely to achieve lower glycosylated hemoglobin levels at 12 weeks if they had higher 25-hydroxyvitamin D levels at 12 weeks (r=-0.4, P=.001).CONCLUSIONS:There was an observed effect of vitamin D supplementation on glycemic control in vitamin D-replete, type 1 diabetes mellitus patients. Further studies are needed to determine if these findings are applicable.

High serum 25-hydroxyvitamin D concentrations are associated with a favorable serum lipid profile

Low serum 25-hydroxyvitamin D (25(OH)D) concentrations are related to increased mortality. One possible explanation could be an association between serum 25(OH)D and serum lipids. The study was performed at the University of Tromsø, Northern Norway. In total, 8018 nonsmoking and 2087 smoking subjects were included in a cross-sectional study performed in 2008, and 1762 nonsmoking and 397 smoking subjects in a longitudinal study from 1994/1995 to 2008. Nonfasting serum 25(OH)D, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), LDL-C/HDL-C ratio and triacylglycerol (TAG) were measured. After adjustment for gender, age, sample month and body mass index in the cross-sectional study, there was a significant increase in serum TC, HDL-C and LDL-C, and a significant decrease in serum LDL-C/HDL-C ratio and TAG across increasing serum 25(OH)D quartiles. For serum HDL-C and TAG in nonsmokers the differences between the means for the highest and lowest serum 25(OH)D quartiles were 6.0 and 18.5%, respectively. In the longitudinal study, an increase in serum 25(OH)D was associated with a significant decrease in serum TAG. There is a cross-sectional association between serum 25(OH)D and serum lipids, and a longitudinal association over 14 years between serum 25(OH)D and TAG, which may contribute to explain the relation between low serum 25(OH)D concentrations and mortality.

Serum 25(OH) Vitamin D and Risk of Breast Cancer: A Nested Case-Control Study from the French E3N Cohort

High 25-hydroxyvitamin D [25(OH)D] serum concentrations have been found to be associated with reduced breast cancer risk. However, few studies have further investigated this relationship according to menopausal status, nor have they taken into account factors known to influence vitamin D status, such as dietary and serum calcium, parathyroid hormone, and estradiol serum levels. We designed a nested case-control study within the French E3N cohort. Cases were women diagnosed with incident breast cancer (n = 636). Controls (n = 1,272) were matched with cases on age, menopausal status at blood collection, age at menopause, and center and year of blood collection. Multivariate logistic regression models were established. We found a decreased risk of breast cancer with increasing 25(OH) vitamin D(3) serum concentrations (odds ratio, 0.73; 95% confidence interval, 0.55-0.96; P trend = 0.02) among women in the highest tertile. We also observed a significant inverse association restricted to women under 53 years of age at blood sampling [odds ratio (T(3) versus T(1)), 0.60; 95% confidence interval, 0.37-0.98; P trend = 0.04]. In premenopausal women, the risk was also decreased, although not significantly. Our findings support a decreased risk of breast cancer associated with high 25(OH) vitamin D(3) serum concentrations, especially in younger women, although we were unable to confirm a direct influence of age or menopausal status. Randomized intervention trials with vitamin D supplementation are required to confirm its benefits on breast cancer risk, but the maintenance of adequate vitamin D levels should be encouraged by public health policy.

Persistent secondary hyperparathyroidism and vertebral fractures in kidney transplantation: Role of calcium-sensing receptor polymorphisms and vitamin D deficiency

Bone morbidity remains a major problem even after successful renal transplantation. We investigated the role of calcium-sensing receptor (CaSR) polymorphisms and 25-hydroxyvitamin D levels on the persistence of secondary hyperparathyroidism (SHPT) and their relationships with vertebral fractures (VFx) in 125 renal allograft recipients transplanted 44 +/- 23 months before. All patients underwent evaluation of the main biochemical parameters of calcium metabolism as well as vertebral and femoral bone density. In 87 patients, CaSR polymorphisms (A986S, R990G, and Q1011E) also were assessed. X-ray images of the lateral spine were obtained in 102 subjects to perform vertebral morphometry. High parathyroid hormone (PTH) and 25-hydroxyvitamin D lower than 80 nmol/L were found in 54% and 97% of patients, respectively, with 40% of these showing vitamin D levels lower than 30 nmol/L. VFx were detected in 57% of the subjects. After multiple adjustments, 25-hydroxyvitamin D, age, and hemodialysis duration, but not CaSR polymorphisms, were found to be significant predictors of high PTH, whereas age and time since transplant were positively related with lower 25-hydroxyvitamin D values. PTH and time since transplant were significantly associated with VFx. Patients with two or more VFx showed serum PTH levels 50% higher than patients without fractures. We therefore conclude that persistent SHPT is a very common feature after renal transplantation and that, unlike CaSR polymorphisms, low 25-hydroxyvitamin D is involved in its pathogenesis. High PTH levels, in turn, are associated with an increased VFx risk, which confirms the need for strategies aimed at lowering serum PTH in this setting as well.

Establishing a Reference Interval for Bone Turnover Markers in 637 Healthy, Young, Premenopausal Women From the United Kingdom, France, Belgium, and the United States

Robust reference intervals are needed for the interpretation of bone turnover markers in large phase III fracture trials. The objectives of the study were to (1) estimate reference intervals for serum bone alkaline phosphatase (bone ALP), serum procollagen type I N propeptide (PINP), serum beta cross-linked C-telopeptides of type I collagen (S-betaCTX), and urinary cross-linked N-telopeptides of type I collagen (U-NTX) in healthy young premenopausal women; (2) examine geographical differences on bone turnover markers; and (3) assess factors known to influence bone turnover and test whether these explain any regional differences. We studied 637 eligible women from four countries that participated in the Horizon-PFT study (United Kingdom, France, Belgium, United States). The women were 30-39 yr of age (mean, 34.6 yr), with regular cyclic menses. Subjects completed a medical and lifestyle questionnaire. Two-sided 95% reference intervals were estimated on transformed values and transformed back to the original scale using the proposed methodology of the International Federation of Clinical Chemistry. S-betaCTX was significantly higher in France relative to the United Kingdom (p = 0.01), and PINP was higher in France (p < 0.001) and Belgium (p = 0.02) relative to the United Kingdom and significantly higher in France relative to the United States (p < 0.01) by ANOVA. Overall, one could associate low bone turnover markers with nonsmoking, use of a contraceptive pill, exercise, being close to the time of ovulation, and having high 25-hydroxyvitamin D levels. Countries differed by these characteristics, and once allowed for in the statistical model, any country differences were attenuated or removed.

Vitamin D in Fracture Prevention and Muscle Function and Fall Prevention

This chapter reviews the potential of vitamin D for the prevention of falls and fractures. Evidence from randomized-controlled trials will be reviewed for both endpoints, as well as epidemiologic data that links higher 25-hydroxyvitamin D (25(OH)D) status to better bone and muscle health. The chapter addresses the evidence of fracture and fall prevention by dose of vitamin D, by type of dwelling and treatment duration. All data considered, this chapter summarizes the compelling dual benefit of vitamin D on fracture reduction by its bone and muscle target, a concept that is reviewed at the onset of the chapter.

Serum Vitamin D and Risk of Pancreatic Cancer in the Prostate, Lung, Colorectal, and Ovarian Screening Trial

Experimental evidence suggests that vitamin D has anticarcinogenic properties; however, a nested case-control study conducted in a population of male Finnish smokers found that higher 25-hydroxyvitamin D [25(OH)D], the best indicator of vitamin D status as determined by the sun and diet, was associated with a significant 3-fold increased risk for pancreatic cancer. We conducted a nested case-control study in the Prostate, Lung, Colorectal, and Ovarian Screening Trial cohort of men and women 55 to 74 years of age at baseline to test whether prediagnostic serum 25(OH)D concentrations were associated with pancreatic cancer risk. Between 1994 and 2006, 184 incident cases of pancreatic adenocarcinoma occurred (follow-up to 11.7 years). Two controls (n = 368) who were alive at the time the case was diagnosed were selected for each case and matched by age, race, sex, and calendar date of blood draw (to control for seasonal variation). We calculated odds ratios (OR) and 95% confidence intervals (95% CI) using conditional logistic regression, adjusting for smoking and body mass index. Vitamin D concentrations were not associated with pancreatic cancer overall (highest versus lowest quintile, >82.3 versus <45.9 nmol/L: OR, 1.45; 95% CI, 0.66-3.15; P trend = 0.49). However, positive associations were observed among subjects with low estimated annual residential solar UBV exposure, but not among those with moderate to high annual exposure (P interaction = 0.015). We did not confirm the previous strong positive association between 25(OH)D and pancreatic cancer; however, the increased risk among participants with low residential UVB exposure is similar.

Independent Association of Low Serum 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D Levels With All-Cause and Cardiovascular Mortality

In cross-sectional studies, low serum levels of 25-hydroxyvitamin D are associated with higher prevalence of cardiovascular risk factors and disease. This study aimed to determine whether endogenous 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels are related to all-cause and cardiovascular mortality. Prospective cohort study of 3258 consecutive male and female patients (mean [SD] age, 62 [10] years) scheduled for coronary angiography at a single tertiary center. We formed quartiles according to 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels within each month of blood drawings. The main outcome measures were all-cause and cardiovascular deaths. During a median follow-up period of 7.7 years, 737 patients (22.6%) died, including 463 deaths from cardiovascular causes. Multivariate-adjusted hazard ratios (HRs) for patients in the lower two 25-hydroxyvitamin D quartiles (median, 7.6 and 13.3 ng/mL [to convert 25-hydroxyvitamin D levels to nanomoles per liter, multiply by 2.496]) were higher for all-cause mortality (HR, 2.08; 95% confidence interval [CI], 1.60-2.70; and HR, 1.53; 95% CI, 1.17-2.01; respectively) and for cardiovascular mortality (HR, 2.22; 95% CI, 1.57-3.13; and HR, 1.82; 95% CI, 1.29-2.58; respectively) compared with patients in the highest 25-hydroxyvitamin D quartile (median, 28.4 ng/mL). Similar results were obtained for patients in the lowest 1,25-dihydroxyvitamin D quartile. These effects were independent of coronary artery disease, physical activity level, Charlson Comorbidity Index, variables of mineral metabolism, and New York Heart Association functional class. Low 25-hydroxyvitamin D levels were significantly correlated with variables of inflammation (C-reactive protein and interleukin 6 levels), oxidative burden (serum phospholipid and glutathione levels), and cell adhesion (vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 levels). Low 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels are independently associated with all-cause and cardiovascular mortality. A causal relationship has yet to be proved by intervention trials using vitamin D.

The association between vitamin D and inflammation with the 6-minute walk and frailty in patients with heart failure.

To identify relationships between anabolic hormones, inflammatory markers, and physical function. Cross-sectional. Outpatient university heart failure program in Connecticut. Sixty patients with an ejection fraction of 40% or less. The 6-minute walk distance and frailty phenotype were measured. The relationship between physical measures of hormones and inflammatory mediators were examined. Linear and ordinal logistic regression analyses were performed for the physical measures. Forty-three men (mean age 77 +/- 9) and 17 women (mean age 78 +/- 12) participated. Longer 6-minute walk distance was correlated with higher 25-hydroxyvitamin D (25OHD) level, and a shorter walk was correlated with higher cortisol: dehydroepiandrosterone sulphate (DHEAS) ratio, high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL6), and intact parathyroid hormone (PTH) (all P<.05). Percentage of free testosterone, DHEAS alone, and N-terminal pro-brain natriuretic peptide (NTpro-BNP) did not correlate with 6-minute walk distance. Higher frailty phenotype score (more frail) was correlated with higher high-sensitivity CRP, higher IL6, and lower 25OHD levels (all P<.05). Linear regression with the 6-minute walk distance as the dependent variable and independent variables of age, sex, percentage of free testosterone, DHEAS, 25OHD, intact PTH, hsCRP, IL6, cortisol/DHEAS ratio, and NTpro-BNP, revealed age, sex, 25OHD and hsCRP to be significant (coefficient of determination=53.5%). Ordinal logistic regression with the frailty phenotype and hormonal levels revealed that age, 25OHD, and hsCRP also predicted frailty status. Twenty-five-hydroxyvitamin D and hsCRP levels may contribute to lower aerobic capacity and frailty in patients with heart failure. A longitudinal study will further define the role of 25OHD and hsCRP on muscle strength and functional decline.

25-Hydroxyvitamin D, insulin resistance, and kidney function in the Third National Health and Nutrition Examination Survey

Previous research has reported reduced serum 25-hydroxyvitamin D levels in patients with chronic kidney disease (CKD), although the relationship between vitamin D status and insulin resistance (IR) in patients with CKD has not been examined in the general population. We examined the association that kidney function, based on glomerular filtration rate (eGFR) estimated from serum creatinine, has with serum levels of 25-hydroxyvitamin D and components of the metabolic syndrome among 14 679 participants in the Third National Health and Nutrition Examination Survey (NHANES III). In this analysis, adjusted mean serum 25-hydroxyvitamin D was significantly lower only in the participants with a severe (15-29 ml/min/1.73 m(2)) decrease in eGFR compared to those with normal kidney function (61.6 vs 73.3 nmol/l, P=0.0063). Serum 25-hydroxyvitamnin D (P=0.0018) and level of kidney function (P=0.0003) were inversely associated, independent of each other, with homeostasis model assessment of insulin resistance (HOMA-IR), adjusting for confounders. Participants with high 25-hydroxyvitamin D levels (>81 nmol/l) had lower HOMA-IR. We conclude that 25-hydroxyvitamin D deficiency is not as prevalent in the US general population with decreased eGFR as previously reported in patients with CKD; and that vitamin D and kidney function have independent inverse associations with IR.

Rise in Prostate-Specific Antigen in Men with Untreated Low-Grade Prostate Cancer Is Slower During Spring-Summer

To test the hypothesis that the rate of rise in prostate-specific antigen (PSA) is slower during the spring-summer than during the rest of the year, we used PSA data from a prospective single-arm cohort study of men who had been followed to characterize a watchful observation protocol with selective delayed intervention for clinically localized, low-to-intermediate grade prostate adenocarcinoma. The rate of PSA increase was calculated as the visit-to-visit slope of log (PSA) against time, from 1 calendar-quarter visit to the next. The nonparametric Friedman test confirmed differences in rate of PSA rise among the calendar quarters (P = 0.041). Post hoc analysis showed the rate of PSA increase during Q2 was significantly slower than in each one of the other calendar quarters (Q1 versus Q2, P = 0.025; Q3 versus Q2, P = 0.002; Q4 versus Q2, P = 0.013), with no differences among quarters Q1, Q3, and Q4. These results are consistent with the vitamin D hypothesis that the higher 25-hydroxyvitamin D levels associated with spring and summer have a desirable effect on prostate biology. The therapeutic implication is that vitamin D supplementation in the range of 2000 IU/d, a dose comparable to the effect of summer, can benefit men monitored for rising PSA.

Effect of Cholecalciferol Plus Calcium on Falling in Ambulatory Older Men and Women

A recent meta-analysis found that cholecalciferol (vitamin D) should reduce falls by more than 20%. However, little is known about whether supplemental cholecalciferol plus calcium citrate malate will lower the long-term risk of falling in men, active older individuals, and older individuals with higher 25-hydroxyvitamin D levels. We studied the effect of 3-year supplementation with cholecalciferol-calcium on the risk of falling at least once in 199 men and 246 women 65 years or older and living at home. Individuals received 700 IU of cholecalciferol plus 500 mg of calcium citrate malate per day or placebo in a randomized double-blind manner. Subjects were classified as less physically active if physical activity was below the median level. Low 25-hydroxyvitamin D levels were classified as those below 32 ng/mL (<80 nmol/L). In 3 years, 55% of women and 45% of men reported at least 1 fall. Mean +/- SD baseline 25-hydroxyvitamin D levels were 26.6 +/- 12.7 ng/mL (66.4 +/- 31.7 nmol/L) in women and 33.2 +/- 14.2 ng/mL (82.9 +/- 34.9) in men. Cholecalciferol-calcium significantly reduced the odds of falling in women (odds ratio [OR], 0.54; 95% confidence interval [CI], 0.30-0.97), but not in men (OR, 0.93; 95% CI, 0.50-1.72). Fall reduction was most pronounced in less active women (OR, 0.35; 95% CI, 0.15-0.81). Baseline 25-hydroxyvitamin D level did not modulate the treatment effect. Long-term dietary cholecalciferol-calcium supplementation reduces the odds of falling in ambulatory older women by 46%, and especially in less active women by 65%. Supplementation had a neutral effect in men independent of their physical activity level.

Relationship Between Serum Parathyroid Hormone Levels, Vitamin D Sufficiency, and Calcium Intake

Adequate vitamin D status for optimum bone health has received increased recognition in recent years; however, the ideal intake is not known. Serum 25-hydroxyvitamin D is the generally accepted indicator of vitamin D status, but no universal reference level has been reached. To investigate the relative importance of high calcium intake and serum 25-hydroxyvitamin D for calcium homeostasis, as determined by serum intact parathyroid hormone (PTH). Cross-sectional study of 2310 healthy Icelandic adults who were divided equally into 3 age groups (30-45 years, 50-65 years, or 70-85 years) and recruited from February 2001 to January 2003. They were administered a semi-quantitative food frequency questionnaire, which assessed vitamin D and calcium intake. Participants were further divided into groups according to calcium intake (<800 mg/d, 800-1200 mg/d, and >1200 mg/d) and serum 25-hydroxyvitamin D level (<10 ng/mL, 10-18 ng/mL, and >18 ng/mL). Serum intact PTH as determined by calcium intake and vitamin D. A total of 944 healthy participants completed all parts of the study. After adjusting for relevant factors, serum PTH was lowest in the group with a serum 25-hydroxyvitamin D level of more than 18 ng/mL but highest in the group with a serum 25-hydroxyvitamin D level of less than 10 ng/mL. At the low serum 25-hydroxyvitamin D level (<10 ng/mL), calcium intake of less than 800 mg/d vs more than 1200 mg/d was significantly associated with higher serum PTH (P = .04); and at a calcium intake of more than 1200 mg/d, there was a significant difference between the lowest and highest vitamin D groups (P = .04). As long as vitamin D status is ensured, calcium intake levels of more than 800 mg/d may be unnecessary for maintaining calcium metabolism. Vitamin D supplements are necessary for adequate vitamin D status in northern climates.

Tanning is associated with optimal vitamin D status (serum 25-hydroxyvitamin D concentration) and higher bone mineral density

Vitamin D is made in the skin on exposure to solar radiation, and it is necessary to optimal skeletal health. Subjects who use a tanning bed that emits ultraviolet B radiation (290-315 nm) are likely to have higher 25-hydroxyvitamin D [25(OH)D] concentrations than do subjects who do not regularly use a tanning bed. The first objective of this study was to ascertain whether subjects who regularly use a tanning bed have higher 25(OH)D concentrations than do subjects who do not use a tanning bed. The second objective was to ascertain whether higher 25(OH)D concentrations correlated positively with bone mineral density. This cross-sectional analysis examined 50 subjects who used a tanning bed at least once a week and 106 control subjects. Each subject gave a blood specimen for measurement of serum 25(OH)D and parathyroid hormone concentrations. Each subject underwent bone mineral density testing of the hip and spine. Subjects who used a tanning bed had serum 25(OH)D concentrations 90% higher than those of control subjects (115.5 +/- 8.0 and 60.3 +/- 3.0 nmol/L, respectively; P <0.001). Subjects who used a tanning bed had parathyroid hormone concentrations 18% lower than those of control subjects (21.4 +/- 1.0 and 25.3 +/- 0.8 pg/mL, respectively; P=0.01). Tanners had significantly higher BMD and z scores at the total hip than did nontanners. The regular use of a tanning bed that emits vitamin D-producing ultraviolet radiation is associated with higher 25(OH)D concentrations and thus may have a benefit for the skeleton.

Higher 25-hydroxyvitamin D concentrations are associated with better lower-extremity function in both active and inactive persons aged ≥60 y

Vitamin D may improve muscle strength through a highly specific nuclear receptor in muscle tissue. We investigated whether there is an association between 25-hydroxyvitamin D [25(OH)D] concentrations and lower-extremity function in ambulatory older persons, whether that association differs by activity level, and, if so, whether there is an identifiable threshold in the association. The study was a population-based survey of the ambulatory US population aged 60 to > or =90 y (n = 4100). Lower-extremity function according to serum 25(OH)D concentrations was assessed by linear regression analyses and regression plots after control for activity level (inactive or active) and several other potential confounders. Separate analyses were performed for the timed 8-foot (ie, 2.4 m) walk test and a repeated sit-to-stand test. The 8-foot walk test compared subjects in the lowest and highest quintiles of 25(OH)D; the latter group had an average decrease of 0.27 s [95% CI: -0.44, -0.09 s (or 5.6%); P for trend < 0.001]. The sit-to-stand test compared subjects in the lowest and highest quintiles of 25(OH)D; the latter group had an average decrease of 0.67 s [95% CI: -1.11, -0.23 s (or 3.9%); P for trend = 0.017]. In the 25(OH)D reference range of 22.5-94 nmol/L, most of the improvement occurred in subjects with 25(OH)D concentrations between 22.5 and approximately 40 nmol/L, and further improvement was seen in the range of 40-94 nmol/L. Stratification by activity level showed no significant effect modification. In both active and inactive ambulatory persons aged > or =60 y, 25(OH)D concentrations between 40 and 94 nmol/L are associated with better musculoskeletal function in the lower extremities than are concentrations < 40 nmol/L.

Vitamin D status, parathyroid function and femoral bone density in an elderly Swedish population living at home

The aim of this study was to determine vitamin D status and bone mineral density (BMD) in elderly, independent Scandinavians. A cross-sectional examination was conducted in a sample of 104 subjects (mean age 84.5 years), for possible correlations among anthropometric data, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, intact parathyroid hormone (PTH) and femoral neck BMD. Daily dietary calcium and vitamin D intakes were below the recommended levels. Five percent of the subjects were taking calcium, and 30% vitamin D supplements. Previous fragility fracture was reported in 30% of the men, and 55% of the women. Higher mean values of serum 25-hydroxyvitamin D (p = 0.03) and femoral neck BMD (p = 0.03) were recorded in subjects spending > or = 3 hours outdoors weekly. Independently of time spent outdoors, subjects taking daily supplements of vitamin D (on average 5 micrograms) had higher 25-hydroxyvitamin D (p < 0.001) levels, without significant changes in femoral neck BMD values. Serum levels of intact PTH (reference range 8-51 ng/L) were elevated in 41%, of which 5% had mild primary hyperparathyroidism. Serum levels of 25-hydroxyvitamin D (reference range 10-65 ng/mL) and 1,25-dihydroxyvitamin D (reference range 15-55 pg/mL) were below the reference ranges in 4% and 5% of the subjects, respectively. When serum levels of 25-hydroxyvitamin D were lower than approximately 30 ng/mL, the serum intact PTH values began to increase from a level of 43 pg/mL. This threshold most probably reflected a more relevant value of vitamin D insufficiency, indicating that 45% of our subjects rather than 4% actually had hypovitaminosis. Multiple regression analysis demonstrated femoral neck BMD to be significantly and positively associated with higher body mass index, male gender, no history of fragility fracture and 25-hydroxyvitamin D (R2 = 0.39). It is concluded that in this sample of healthy elderly people who regularly spend time outdoors, vitamin D levels leading to secondary hyperparathyroidism seem to be a major cause of osteoporosis. Correcting chronic dietary calcium deficiency is likely to eliminate another factor contributing to poor bone health.

Low total body bone mineral content and high bone resorption in Korean winter-born versus summer-born newborn infants

Seasonal differences in newborn total body bone mineral content (TBBMC) have not been studied, particularly in relation to alterations in vitamin D status in winter. In vitamin D deficiency bone resorption may be high and bone mineralization low. Bone resorption may be assessed by serum cross-linked carboxyterminal telopeptide of type I collagen (ICTP) measures. Because vitamin D supplements throughout pregnancy are uncommon in Korea, we hypothesized that in Korean winter newborns, TBBMC is low and serum ICTP high from high bone resorption and low 25-hydroxyvitamin D (25-OHD) compared with those in summer newborns. Seventy-one Korean term infants were studied prospectively in summer (July through September, n = 37) versus winter (January through March, n = 34); TBBMC was measured before 3 days of age by dual-energy x-ray absorptiometry. Significant seasonal differences were found: winter newborns had 6% lower TBBMC (least squares means ± SD; 86.7 ± 7.7 gm vs 93.9 ± 7.8 gm, p = 0.0002), lower cord serum 25-OHD (10.7 ± 8 nm vs 30 ± 15 nm, p = 0.0001) and 1,25-dihydroxyvitamin D, and higher ICTP (96.4 ± 20.3 μg/L vs 74.8 ± 24 μg/L, p = 0.0002) and calcium than summer newborns. TBBMC correlated with serum 25-OHD ( r = 0.243, p = 0.047) and inversely with ICTP ( r = –0.333, p = 0.008). We suggest that in Korea low maternal vitamin D status in winter results in marked reduction in newborn TBBMC. (J Pediatr 1998;132:421-5)

Age-dependent vitamin D status and vertebral condition of white women living in Curaçao (The Netherlands Antilles) as compared with their counterparts in The Netherlands

Plasma vitamin D metabolites and parathyroid hormone concentrations of two groups of white women, aged 26-46 and 63-83 y, in Curaçao were studied to evaluate the effect of yearlong abundant sunlight on frequency of vertebral compression fractures in elderly women. 25-Hydroxyvitamin D of the younger group (median, 116 nmol/L) was higher than that of the older group (75 nmol/L). Both groups had higher 25-hydroxyvitamin D compared with approximately age-matched counterparts in The Netherlands during autumn and winter (50 and 25 nmol/L, respectively). Similar differences were found for 1,25-dihydroxyvitamin D, although to a lesser extent. Parathyroid hormone concentrations of older women in Curaçao (4.3 pmol/L) were higher than those of the younger women (2.3 pmol/L). Roentgenographic analyses of the spines of the older women did not show vertebral compression fractures commonly encountered in women living at higher latitudes. Uninterrupted high plasma concentrations of vitamin D metabolites may reduce vertebral compression fractures in postmenopausal white women.

Expression of a high km 25-hydroxyvitamin D-1α-hydroxylase in a human hepatoma cell line HEP G2

Expression of a high km 25-hydroxyvitamin D-1α-hydroxylase in a human hepatoma cell line HEP G2