Interpreting the Laboratory Reports for Vit D

Importance for Vit D estimation has increased in the recent years due to its link to various diseases. Measurements of Vit D by different diagnostic laboratories is however not uniform. There is variation pertaining to assay methodology and also variation in the measurement of different metabolites of Vit D. There are also various confounders which influence Vit D assays and which in most instances are overlooked. Also a matter of concern regarding Vit D assays is the lack of assay standardisation. These factors contribute to the variation in the reports generated by the diagnostic laboratories. Therefore interpretation of Vit D reports needs proper understanding of these interfering factors and further reports need to be correlated substantially with the clinical findings.

Technical and clinical evaluation of the VITROS® Immunodiagnostic Products 25-OH Vitamin D Total Assay--comparison with marketed automated immunoassays and a liquid chromatography-tandem mass spectrometry method

BACKGROUND

The study was conducted to evaluate the technical and clinical performance of the VITROS® Immunodiagnostic Products 25-OH Vitamin D Total Assay, and compare it with the performance of five marketed automated assays and a liquid chromatography/mass spectrometry reference method (LC-MS/MS).

METHODS

Three hundred patient serum samples were used to compare the correlation of the VITROS® 25-OH Vitamin D Total Assay with both the other immunoassays and the LC-MS/MS method, using Passing-Bablok regression and Bland-Altman analyses. Concordance of the diagnosis of vitamin D status was calculated to test the agreement between the different assays. In addition, samples containing vitamin D2 were used to test the assay's ability to detect the D2 form of the vitamin.

RESULTS AND CONCLUSIONS

These results from the VITROS® 25-OH Vitamin D Total Assay generally correlated well with those from most of the marketed immunoassays. Cross-reactivity of the D2 form was calculated as being close to 100%. Additionally, we found substantial variability in performance amongst the various assays, which suggests the need for optimisation and recalibration of commercial methods.

Case report: Three patients with substantial serum levels of 3-epi-25(OH)D including one with 3-epi-25(OH)D2 while on high-dose ergocalciferol

CONTEXT

We report the presence of substantial concentrations of 3-epi-25(OH)D3 in two patients and a third patient with 3-epi-25(OH)D2.

PATIENTS

The first patient, a 66-year-old female receiving cholecalciferol 4000 IU daily was originally found to have 53 ng/mL of 25(OH)D3 and almost an equal amount of 3-epi-25(OH)D3. Subsequently, the patient had four additional samples, each of which has similar levels of both 25(OH)D3 and 3-epi-25(OH)D3. The second patient, a 7-year-old male receiving cholecalciferol 1000 IU daily, had a 25(OH)D3 concentration of 37 ng/mL and 3-epi-25(OH)D3 of approximately 10 ng/mL. The third and most intriguing patient, a 55-year-old female was receiving ergocalciferol 50,000 IU twice weekly for approximately 3 months, at which time her serum 25(OH)D2 was 64 ng/mL and her 3-epi-25(OH)D2 was approximately 32 ng/mL. This patient's physician changed her vitamin D therapy to cholecalciferol 1000 IU daily, discontinuing ergocalciferol, and a second specimen was collected 5 months later. Analysis of this last specimen found both 25(OH)D3 and 25(OH)D2 at concentrations of 12 and 24 ng/mL respectively, plus corresponding 3-epimer peaks for both 25(OH)D3 and 25(OH)D2 observed chromatographically.

CONCLUSION

The presence of a substantial concentration of 3-epi-25(OH)D in these three patients documents that one cannot assume 3-epi is a trivial metabolite of 25(OH)D for all patients. In addition, the appearance of 3-epi-25(OH)D3 when the last patient changed her vitamin D supplementation from ergocalciferol to cholecalciferol demonstrates that the 3-epimer is probably an endogenous metabolite of 25(OH)D in humans.

Vitamin D2 supplementation amplifies eccentric exercise-induced muscle damage in NASCAR pit crew athletes

This study determined if 6-weeks vitamin D₂ supplementation (vitD₂, 3800 IU/day) had an influence on muscle function, eccentric exercise-induced muscle damage (EIMD), and delayed onset of muscle soreness (DOMS) in National Association for Stock Car Auto Racing (NASCAR) NASCAR pit crew athletes. Subjects were randomized to vitD₂ (n = 13) and placebo (n = 15), and ingested supplements (double-blind) for six weeks. Blood samples were collected and muscle function tests conducted pre- and post-study (leg-back and hand grip dynamometer strength tests, body weight bench press to exhaustion, vertical jump, 30-s Wingate test). Post-study, subjects engaged in 90 min eccentric-based exercise, with blood samples and DOMS ratings obtained immediately after and 1- and 2-days post-exercise. Six weeks vitD₂ increased serum 25(OH)D₂ 456% and decreased 25(OH)D₃ 21% versus placebo (p < 0.001, p = 0.036, respectively), with no influence on muscle function test scores. The post-study eccentric exercise bout induced EIMD and DOMS, with higher muscle damage biomarkers measured in vitD₂ compared to placebo (myoglobin 252%, 122% increase, respectively, p = 0.001; creatine phosphokinase 24 h post-exercise, 169%, 32%, p < 0.001), with no differences for DOMS. In summary, 6-weeks vitD₂ (3800 IU/day) significantly increased 25(OH)D₂ and decreased 25(OH)D₃, had no effect on muscle function tests, and amplified muscle damage markers in NASCAR pit crew athletes following eccentric exercise.

Clinical review: The role of the parent compound vitamin D with respect to metabolism and function: Why clinical dose intervals can affect clinical outcomes

CONTEXT

There is no doubt that vitamin D must be activated to the hormonal form 1,25-dihydroxyvitamin D to achieve full biological activity or that many tissues participate in this activation process-be it endocrine or autocrine. We believe that not only is 25-hydroxyvitamin D important to tissue delivery for this activation process, but also that intact vitamin D has a pivotal role in this process.

OBJECTIVE

In this review, evidence on the vitamin D endocrine/autocrine system is presented and discussed in relation to vitamin D-binding protein affinity, circulating half-lives, and enzymatic transformations of vitamin D metabolites, and how these affect biological action in any given tissue.

CONCLUSIONS

Circulating vitamin D, the parent compound, likely plays an important physiological role with respect to the vitamin D endocrine/autocrine system, as a substrate in many tissues, not originally thought to be important. Based on emerging data from the laboratory, clinical trials, and data on circulating 25-hydroxyvitamin D amassed during many decades, it is likely that for the optimal functioning of these systems, significant vitamin D should be available on a daily basis to ensure stable circulating concentrations, implying that variation in vitamin D dosing schedules could have profound effects on the outcomes of clinical trials because of the short circulating half-life of intact vitamin D.

Influence of estrogen therapy on calcium, phosphorus, and other regulatory hormones in postmenopausal women: the MESA study

BACKGROUND

Estrogen therapy (ET) is associated with lower serum calcium and phosphorus concentrations and is known to increase bone mineral density (BMD). Other biomarkers of mineral metabolism may help understand the biological basis of these actions.

METHODS

We studied 2767 postmenopausal women in the Multi-Ethnic Study of Atherosclerosis, 862 (31%) of whom were using ET. We measured serum concentrations of calcium, phosphorus, 25-hydroxyvitamin D, 24,25-dihydoxyvitamin D, and fibroblast growth factor-23 and urinary fractional excretion of calcium (FEca) and phosphorus (FEphos). We examined the associations of ET with each biomarker. In addition, we tested whether the adjustment for biomarkers attenuated the association of ET with lumbar BMD measured by abdominal computed tomography in a subset of 810 women.

RESULTS

In adjusted models, women who used ET were younger in age [62 (SD 8) vs 66 (9) y, P < .001], had lower mean serum calcium [-13 mg/dL (95% confidence interval [CI] -0.17, -0.10), P < .001] and lower FEca [-0.15% (95% CI -0.21, -0.09), P < .001]. Mean serum phosphorus was lower [-0.19 mg/dL (95% CI -0.23, -0.15), P < .001] and FEphos [0.56% (95% CI 0.16, 0.96), P = .007] was higher in women on ET. Mean 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D were higher [1.52 ng/dL (95% CI 0.57, 2.47), P = .002, and 0.26 ng/mL (95% CI 0.03, 0.48), P = .03, respectively] in women who used ET. Mean PTH and fibroblast growth factor-23 did not differ significantly by the use of ET. ET use was strongly associated with higher lumbar BMD [12.75 mg/cm³ (95% CI 7.77-17.73), P < .001]; however, mineral metabolism measures did not meaningfully alter this association.

CONCLUSIONS

In a multiethnic cohort of postmenopausal women, ET use was associated with lower serum calcium, lower FEca, lower serum phosphorus, and higher FEphos, suggesting these associations are attributable to increased calcium intake into bone and increased urinary phosphorus excretion. ET use was also associated with greater concentrations of vitamin D metabolites. ET-associated differences in these mineral metabolism measures did not meaningfully attenuate the strong association between ET use and lumbar BMD.

Bioavailability of vitamin D(2) and D(3) in healthy volunteers, a randomized placebo-controlled trial

BACKGROUND

The bioequivalence of the different forms of vitamin D, ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3), has been questioned. Earlier studies have suggested that vitamin D2 is less biologically active than vitamin D3.

OBJECTIVE AND DESIGN

In a parallel study, we tested the effects of supplementation with 50-μg/d doses of vitamin D2 or D3 or a placebo over a period of 8 weeks on 25(OH)D2, 25(OH)D3, their sum 25(OH)D (primary outcome variables), and PTH in healthy volunteers applying a double-blind, randomized study design. The study was conducted during the winter of 2012 in Halle (Saale), Germany, at latitude 51°47N, when UVB irradiation is virtually absent. Blood samples for the determinations of vitamin D status and PTH were collected at baseline and after 4 and 8 weeks of supplementation.

RESULTS

In the placebo group (n = 19), 25(OH)D3 decreased from 39.4 ± 14.2 to 31.1 ± 12.4 nmol/L after 8 weeks (P < .01). In the vitamin D3 group (n = 42), the concentrations of 25(OH)D3 increased from 41.5 ± 22.8 nmol/L at baseline to 88.0 ± 22.1 nmol/L after 8 weeks (P < .01). In the group receiving vitamin D2 (n = 46), the 25(OH)D2 concentrations increased significantly, whereas the 25(OH)D3 concentration fell from 36.4 ± 13.3 nmol/L at baseline to 16.6 ± 6.3 nmol/L after 8 weeks (P < .01). The total 25(OH)D was not different between the groups at baseline but differed significantly between the groups after 4 and 8 weeks (P < .001).

CONCLUSIONS

Vitamin D3 increases the total 25(OH)D concentration more than vitamin D2. Vitamin D2 supplementation was associated with a decrease in 25(OH)D3, which can explain the different effect on total 25(OH)D.

The effects of vitamin D₂ or D₃ supplementation on glycaemic control and related metabolic parameters in people at risk of type 2 diabetes: protocol of a randomised double-blind placebo-controlled trial

BACKGROUND

The global prevalence of type 2 diabetes is increasing. Effective strategies to address this public health challenge are currently lacking. A number of epidemiological studies have reported associations between low concentrations of 25-hydroxy vitamin D and the incidence of diabetes, but a causal link has not been established. We investigate the effect of vitamin D supplementation on the metabolic status of individuals at increased risk of developing type 2 diabetes.

METHODS/DESIGN

In a randomised double-blind placebo-controlled trial individuals identified as having a high risk of type 2 diabetes (non-diabetic hyperglycaemia or positive diabetes risk score) are randomised into one of three groups and given 4 doses of either placebo, or 100,000 IU Vitamin D₂ (ergocalciferol) or 100,000 IU Vitamin D₃ (cholecalciferol) at monthly intervals. The primary outcome measure is the change in glycated haemoglobin level between baseline and 4 months. Secondary outcome measures include blood pressure, lipid levels, apolipoproteins, highly sensitive C-reactive protein, parathyroid hormone (PTH) and safety of supplementation. and C-reactive protein. The trial is being conducted at two sites (London and Cambridge, U.K.) and a total of 342 participants are being recruited.

DISCUSSION

Trial data examining whether supplementation of vitamin D improves glycaemic status and other metabolic parameters in people at risk of developing type 2 diabetes are sparse. This trial will evaluate the causal role of vitamin D in hyperglycaemia and risk of type 2 diabetes. Specific features of this trial include recruitment of participants from different ethnic groups, investigation of the relative effectiveness and safety of vitamin D₂ and D₃ and an evidence based approach to determination of the dose of supplementation.

TRIAL REGISTRATION

EudraCT2009-011264-11; ISRCTN86515510.

Long-term bioavailability after a single oral or intramuscular administration of 600,000 IU of ergocalciferol or cholecalciferol: implications for treatment and prophylaxis

CONTEXT

We previously showed that a single high dose of oral (po) cholecalciferol (D₃) sharply increases serum 25-hydroxyvitamin D [25(OH)D].

OBJECTIVE

We evaluated the long-term bioavailability and metabolism of a single po or intramuscular (im) high dose of ergocalciferol (D₂) or D₃.

DESIGN

This was a prospective intervention study.

SETTING

The study was conducted in an ambulatory care setting.

PATIENTS

Participants were 24 subjects with hypovitaminosis D.

INTERVENTIONS

A single dose of 600,000 IU of po or im D₂ or D₃ was administered.

MAIN OUTCOME MEASURES

Serum 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)₂D] were measured at baseline and at days 30, 60, 90, and 120 by RIA. Serum 1,25(OH)₂D₂, 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], 24,25-hydroxyvitamin D₂ [24,25(OH)D₂], and 24,25-hydroxyvitamin D₃ [24,25(OH)D₃] were measured by liquid chromatography-tandem mass spectrometry in a subgroup of patients receiving the po formulations.

RESULTS

The areas under the curve of 25(OH)D after D₃ were significantly higher than those after D₂ (P < .0001). Serum 25(OH)D basal difference significantly increased at day 30 with po D₂ and D₃ (P < .01 and P < .0001) and up to day 90 with po D₃ (P < .01). The im formulations produced a slow increased, and values peaked at day 120 relative to the other time points (P < .0001). We found a decrease in 1,25(OH)₂D at day 30 (P < .05) and up to day 120 (P < .001) and an increase in 1,25(OH)₂D₂ at day 30 (P < .01) and up to day 120 (P < .01) after po D₂. Oral D₂ and D₃ produced increases in 24,25(OH)D₂ and 24,25(OH)D₃, respectively, at day 30 (P < .001).

CONCLUSIONS

A po dose of 600,000 IU of D₂ or D₃ is initially more effective in increasing serum 25(OH)D than the equivalent im dose and is rapidly metabolized. Our RIA assay for 1,25(OH)₂D may not recognize 1,25(OH)₂D₂.

Mineral metabolism and cortical volumetric bone mineral density in childhood chronic kidney disease

CONTEXT

The relationships among cortical volumetric bone mineral density (CortBMD) and comprehensive measures of mineral metabolism have not been addressed in chronic kidney disease (CKD).

OBJECTIVE

The aim of the study was to identify the determinants of CortBMD in childhood CKD. A secondary objective was to assess whether CortBMD was associated with subsequent fracture.

DESIGN AND PARTICIPANTS

This prospective cohort study included 171 children, adolescents, and young adults (aged 5-21 years) with CKD stages 2-5D at enrollment and 89 1 year later.

OUTCOMES

Serum measures included vitamin D [25-hydroxyvitamin D (25[OH]D), 1,25-dihydroxyvitamin D (1,25(OH)₂D), 24,25-dihydroxyvitamin D], vitamin D-binding protein, intact PTH, fibroblast growth factor 23, calcium, and phosphorus. Tibia quantitative computed tomography measures of CortBMD were expressed as sex-, race-, and age-specific Z-scores based on 675 controls. Multivariable linear regression identified the independent correlates of CortBMD Z-scores and the change in CortBMD Z-scores.

RESULTS

Lower calcium (β = .31/1 mg/dL, P = .01) and 25(OH)D (β = .18/10 ng/mL, P = .04) and higher PTH (β = -.02/10%, P = .002) and 1,25(OH)₂D (β = -.07/10%, P < .001) were independently associated with lower CortBMD Z-scores at baseline. The correlations of total, free, and bioavailable 25(OH)D with CortBMD did not differ. Higher baseline 1,25(OH)₂D (P < .05) and greater increases in PTH (P < .001) were associated with greater declines in CortBMD Z-scores. Greater increases in calcium concentrations were associated with greater increases in CortBMD Z-scores in growing children (interaction P = .009). The hazard ratio for fracture was 1.75 (95% confidence interval 1.15-2.67; P = .009) per SD lower baseline CortBMD.

CONCLUSIONS

Greater PTH and 1,25(OH)₂D and lower calcium concentrations were independently associated with baseline and progressive cortical deficits in childhood CKD. Lower CortBMD Z-score was associated with increased fracture risk.

Serum concentrations of 1,25-dihydroxyvitamin D2 and 1,25-dihydroxyvitamin D3 in response to vitamin D2 and vitamin D3 supplementation

OBJECTIVE

The purpose of this study was to determine 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and 1,25-dihydroxyvitamin D2 [1,25(OH)2D2] levels in healthy adults consuming 1000 IU vitamin D2 or vitamin D3 per day for 11 weeks.

SUBJECTS AND DESIGN

Blood from 34 healthy male and female adults, aged 18 to 79 years, from a placebo-controlled, double-blind study who received a placebo, 1000 IU vitamin D3, or 1000 IU vitamin D2 daily for 11 weeks at end of winter was analyzed. Serum levels of 25-hydroxyvitamin D2, 25-hydroxyvitamin D3, 1,25(OH)2D2, and 1,25(OH)2D3 were determined by liquid chromatography-tandem mass spectroscopy.

RESULTS

Of the adults, 82% were vitamin D insufficient (serum 25-hydroxyvitamin D [25(OH)D <30 ng/mL]) at the start of the study. Administration of vitamin D2 and vitamin D3 induced similar increases in total 25(OH)D as well as in 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3, respectively. Compared with placebo and adjusting for baseline levels, 1000 IU daily of vitamin D2 was associated with a mean increase of 7.4 pg/mL (95% confidence interval, 4.4-10.3) in 1,25(OH)2D2, which was accompanied by a mean decrease of 9.9 pg/mL (-15.8 to -4.0) in 1,25(OH)2D3. No such differences accompanied administration of 1000 IU daily of vitamin D3.

CONCLUSION

Vitamin D2 and vitamin D3 were effective in raising and maintaining total serum concentrations of 25(OH)D. Ingestion of vitamin D2 also resulted in an increase in serum concentrations of 1,25(OH)2D2. This increase was accompanied by a comparable decrease in serum concentrations of 1,25(OH)2D3; therefore, the total 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations did not significantly change after 11 weeks compared with baseline levels. Ingestion of vitamin D3 did not alter serum concentrations of 1,25(OH)2D3 or total 1,25(OH)2D. Therefore, ingestion of 1000 IU vitamin D2 or vitamin D3 for 11 weeks was effective in raising total serum concentrations of 25(OH)D as well as sustaining serum concentrations of total 1,25(OH)2D.

Serum 24,25-dihydroxyvitamin D concentrations in osteogenesis imperfecta: relationship to bone parameters

BACKGROUND

Several studies suggest that 24,25-dihydroxyvitamin D [24,25(OH)₂D] may have an effect on bone mass and metabolism.

OBJECTIVE

We evaluated the relationship between serum 24,25(OH)₂D levels and bone density and bone metabolism in children with a primary bone disorder-osteogenesis imperfecta (OI).

MATERIALS AND METHODS

The study included 132 patients (age, 1.1 to 17.9 yr; 67 girls) with OI types I, III, or IV who had not received bisphosphonate treatment at the time of analysis.

RESULTS

Serum 24,25(OH)₂D levels were significantly higher in OI type III than in OI type I or IV. Serum 24,25(OH)₂D concentrations were positively correlated with serum 25-hydroxyvitamin D (25OHD) levels and negatively correlated with serum PTH levels, and were not correlated with serum 1α,25-dihydroxyvitamin D [1,25(OH)₂D]. The ratio between serum 24,25(OH)₂D and 25OHD was negatively correlated with age and was independent of serum 25OHD concentrations. Regression analysis revealed that OI severity (P = 0.04), serum 25OHD levels (P < 0.001), and serum PTH concentrations (P = 0.045), but not age, gender, or serum 1,25(OH)₂D, were independent predictors of serum 24,25(OH)₂D levels. No correlation was found between serum 24,25(OH)₂D levels or the ratio between serum 24,25(OH)₂D and 25OHD and lumbar spine bone mineral density z-scores or bone marker levels (serum osteocalcin and urinary collagen type I N-telopeptide) after adjusting for OI type, age, and gender.

CONCLUSION

Patients with more severe OI type had higher 24,25(OH)₂D serum levels and higher serum 24,25(OH)₂D to 25OHD ratios, suggesting an increased 25OHD-24-hydroxylase activity.

Prospective evaluation of bone markers, parathormone and 1,25-(OH)₂ vitamin D in HIV-positive patients after the initiation of tenofovir/emtricitabine with atazanavir/ritonavir or efavirenz

BACKGROUND

Increased risk of fractures and osteoporosis have been associated with the use of antiretroviral drugs. There is a paucity of prospective evaluations of bone markers after the initiation of drugs currently recommended to treat HIV infection and results on the evolution of these markers are conflicting. Lastly, the effect of tenofovir on 1,25-(OH)₂ vitamin D is uncertain.

METHODS

We performed a prospective study on the evolution of bone markers, parathormone and 1,25-(OH)₂ vitamin D before and after standard antiretroviral regimens. This was a sub-study of a trial conducted in antiretroviral-naïve patients randomized to tenofovir + emtricitabine in combination with either atazanavir/ritonavir (ATV/r) or efavirenz (EFV). Follow-up lasted 48 weeks. The following bone markers were analyzed: C-terminal cross-laps (CTx), osteocalcin (OC), osteoprotegerin (OPG), and receptor activator of nuclear factor κB ligand (RANKL). Mixed-factorial analysis of variance with random-coefficient general linear model was used to compare their trends over time and linear multivariable regression was performed with a backward selection method to assess predictors of their variations from baseline to week 48. Trends of parathormone and 1,25-(OH)₂ vitamin D were also evaluated.

RESULTS

Seventy-five patients were studied: 33 received EFV and 42 ATV/r. Significant increases were found for all markers except for RANKL. There was a significant direct association between CTx and OC increases. Multivariable analysis showed that higher glomerular filtration rate (estimated through cystatin C clearance) predicted greater OPG increase, while older age, higher HIV RNA at baseline and use of ATV/r predicted greater CTx increase. A significant increase of parathormone accompanied the evolution of the study markers. 1,25-(OH)₂ vitamin D remained stable, though a seasonality variation was demonstrated.

CONCLUSIONS

These data demonstrate CTx increase (bone resorption marker) corresponding to OC increase (bone formation marker) early upon HAART initiation. Moreover, predictors of bone marker increases have been suggested, possibly indicating that a stricter monitoring of bone health and pro-active interventions are needed in older patients, those with higher HIV RNA, prescribed ATV/r rather than EFV, and with decreased renal function at baseline. Further studies are needed to clarify the mechanisms responsible for up-regulation of bone turnover markers, as well as to understand if and what markers are best correlated or predictive of pathological fractures.

Evaluation of bone markers in hypophosphatemic rickets/osteomalacia

N-terminal propeptide of type I procollagen (PINP) is a marker of newly formed type I collagen. However, its role in hypophosphatemic rickets/osteomalacia has not yet been established. Metabolic bone markers were examined in patients with oncogenic osteomalacia (OOM) and X-linked hypophosphatemic rickets (XLH), and in healthy controls. OOM and XLH patients were found to have hypophosphatemia secondary to elevated levels of serum fibroblast growth factor 23 (FGF-23). OOM patients had reduced levels of 1,25-dihydroxy vitamin D (1,25D) compared with XLH patients and healthy controls, despite attenuation of the reduction in these levels in the XLH patients secondary to active vitamin D supplementation. In contrast to patients with XLH, OOM patients showed a significant increase in serum PINP, which is suggestive of accelerated bone matrix formation. Bone alkaline phosphatase (BAP) and the BAP/PINP ratio were also increased in OOM but not in XLH patients, suggesting the presence of a disturbance in bone mineralization in OOM. Long-term supplementation of active form vitamin D and inorganic phosphate (IP) may have attenuated the defect in bone mineralization in the XLH patients, resulting in the normalization of PINP, BAP, and the BAP/PINP ratio. The present results suggest that, as with BAP, PINP is an appropriate metabolic bone marker in the assessment of hypophosphatemic rickets/osteomalacia.

Bioavailability of vitamin D in malnourished adolescents with anorexia nervosa

CONTEXT

Young women with anorexia nervosa (AN) have a normal vitamin D status. The bioavailability of vitamin D during malnutrition is unknown.

OBJECTIVE

The objective of the study was to examine the serum response to oral ergocalciferol in AN.

DESIGN/SETTING

This was a prospective cohort study, conducted in 2007-2009 at a tertiary care center.

PATIENTS/INTERVENTIONS

Twelve adolescents with AN (age 19.6 ± 2.0 yr, body mass index 16.5 ± 1.4 kg/m²) and 12 matched healthy controls (20.0 ± 2.4 yr, 22.7 ± 1.0 kg/m²) received one baseline 50,000 IU oral dose of ergocalciferol.

MAIN OUTCOMES

Serum D₂, D₃, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D, collected before ingestion, at 6 and 24 h and weekly for 4 wk, and body composition measures were measured.

RESULTS

The AN group was severely malnourished (77.2 ± 6.3% median body weight), whereas the control group was normal weighted (106.2 ± 6.2%). From a common baseline D₂ (1.5 ± 1.6 nmol/liter, P =0.34) the groups diverged (time × group interaction P = 0.04), peaking at 70 ± 34 nmol/liter at 6 h in controls compared with 43 ± 28 nmol/liter in AN subjects (P = 0.008). The D₂ trajectories converged at 24 h (57 nmol/liter, P = 0.98) and returned to near baseline at 1 wk. Baseline D₃ was higher in AN subjects (12.1 ± 9.6 vs. 3.1 ± 2.3 nmol/liter, P < 0.001) and remained higher throughout. 25-Hydroxyvitamin D followed a common trajectory (time × group interaction P = 0.15), rising to 45 ± 10 nmol/liter at 24 h but returning to baseline by wk 3 (P = 0.36). Correlating vitamin D levels with fat measures (body mass index, body fat) produced similar findings.

CONCLUSIONS

Despite severe malnutrition, young women with AN had a similar bioavailability of oral ergocalciferol as the healthy-weighted controls. Vitamin D dosing for patients suffering from malnutrition may not differ from that for normal-weighted adolescents.

Determination of vitamins A, D and E in a small volume of human plasma by a high-throughput method based on liquid chromatography/tandem mass spectrometry

We have developed an automated high-throughput assay for the determination of vitamin A (retinol), ergocalciferol (25-OH D2), cholecalciferol (25-OH D3) and vitamin E (α-tocopherol) in a small volume of human plasma. Sample preparation involved mixing 50 μL of plasma with 100 μL of ethanol containing isotope-labelled internal standards, followed by mixing with isooctane/chloroform (3:1, 300 μL). The organic phase was evaporated, and the sample reconstituted in 50 μL methanol. The analysis was performed using reversed-phase liquid chromatography with a gradient mobile phase containing water, methanol and ammonium formate. Chromatographic run-time was 5 min, and positive mode electrospray tandem mass spectrometry (MS/MS) was used for detection. The limits of detection were 0.10 μM for all-trans retinol and 3.3 nM for 25-OH D2 and 25-OH D3. Recoveries were 91.9-105.0%, and within- and between-day coefficients of variance (CVs) 2.4-5.3 and 3.1-8.2, respectively. The assay is presently being used in large-scale studies.

Circulating 25-hydroxyvitamin D levels and frailty status in older women

CONTEXT

Vitamin D deficiency and frailty are common with aging, but the association between these conditions is uncertain.

OBJECTIVE

To determine the association between 25-hydroxyvitamin D (25(OH)D) levels and prevalent and incident frailty status among older women.

DESIGN

Cross-sectional and longitudinal analyses of a prospective cohort study.

SETTING

Four U.S. centers.

PARTICIPANTS

6307 women aged≥69 years.

MAIN OUTCOME MEASURES

Frailty status classified as robust, intermediate stage, or frail at baseline; and robust, intermediate stage, frail, or dead (all-cause mortality) at follow-up an average of 4.5 years later.

RESULTS

At baseline, there was a U-shaped association between 25(OH)D level and odds of frailty with the lowest risk among women with levels 20.0-29.9 ng/ml (referent group). Compared with this group, the odds of frailty were higher among those with levels<15.0 ng/ml [multivariable odds ratio (MOR) 1.47, 95% confidence interval (CI), 1.19-1.82], those with levels 15.0-19.9 ng/ml (MOR 1.24, 95% CI 0.99-1.54), and those with levels≥30 ng/ml (MOR 1.32, 95% CI 1.06-1.63). Among 4551 nonfrail women at baseline, the odds of frailty/death (vs. robust/intermediate) at follow-up appeared higher among those with levels 15.0-19.9 ng/ml (MOR 1.21, 95% CI 0.99-1.49), but the CI overlapped 1.0. The odds of death (vs. robust/intermediate/frail at follow-up) was higher among those with levels<15.0 ng/ml (MOR 1.40, 95% CI 1.04-1.88) and those with levels 15.0-19.9 ng/ml (MOR 1.30, 95% CI 0.97-1.75), although the latter association did not quite reach significance.

CONCLUSION

Lower (<20 ng/ml) and higher (≥30 ng/ml) levels of 25(OH)D among older women were moderately associated with a higher odds of frailty at baseline. Among nonfrail women at baseline, lower levels (<20 ng/ml) were modestly associated with an increased risk of incident frailty or death at follow-up.

Treatment and prevention of vitamin D insufficiency in cystic fibrosis patients: comparative efficacy of ergocalciferol, cholecalciferol, and UV light

BACKGROUND

The optimal treatment for correcting or preventing vitamin D insufficiency in cystic fibrosis (CF) patients has not been established.

OBJECTIVE

The aim of the study was to assess the relative efficacy of three modes of vitamin D therapy: cholecalciferol (D3), ergocalciferol (D2), and UV light in raising or maintaining 25(OH)D levels above 30 ng/ml.

DESIGN

Thirty adult CF subjects with vitamin D insufficiency were randomized into one of three treatment arms: D3, D2, or UV light. Subjects randomized to D3 or D2 ingested 50,000 IU of vitamin D weekly, and those randomized to UV exposed their skin to UV light from a lamp five times a week. Serum was collected for 25(OH)D and PTH at baseline and at 12 wk.

RESULTS

Treatment with D3 and D2 raised 25(OH)D levels significantly, from a mean of 21.2 +/- 10.18 to 47.1 +/- 20.5 ng/ml (P < 0.001) and 24.4 +/- 10.3 to 32.7+/- 9.7 ng/ml (P = 0.01), with 100% and 60% reaching 25(OH)D levels above 30 ng/ml, respectively. Treatment with UV did not raise 25(OH)D levels significantly; however, only 55% of subjects were adherent with UV therapy.

CONCLUSION

This study demonstrates that CF subjects are able to achieve or maintain optimal vitamin D status (>30 ng/ml) with two oral regimens of either D3 or D2 treatment, the former being more efficacious. A confounding variable for this observation is the fact that the D3 and D2 capsules contained different carriers, powder-based vs. oil-based, respectively. UV therapy did not alter vitamin D status, possibly due to poor adherence to UV therapy.

Ectopic thymic parathyroid adenoma and vitamin D deficiency rickets: a 5-year-follow-up case report and review of literature

Sixteen patients with primary hyperparathyroidism presenting as rickets have so far been reported in the English literature. However, no report of an ectopic thymic parathyroid adenoma presenting as rickets has been published. We report a 14-year-old Caucasian American, wheelchair-ridden male who presented with signs and symptoms suggestive of vitamin D deficiency rickets subsequently confirmed by laboratory and radiological findings. Following the intramuscular administration of 125,000 U ergocalciferol (vitamin D2), he developed hypercalcemia with persistently elevated parathyroid hormone (PTH) levels suggestive of primary hyperparathyroidism. Sestamibi scan demonstrated significant uptake in the superior chest, without uptake at the normal parathyroid glands location. Surgical exploration revealed normal parathyroid glands and a thymic mass, which was removed and confirmed by pathology to be a parathyroid adenoma. With subsequent oral ergocalciferol solution and calcium carbonate therapies, the patient's symptoms resolved, blood chemistries normalized, and radiological evidence of rickets significantly improved. To our knowledge, this is the first case of an ectopic thymic parathyroid adenoma in a patient presenting with rickets. Our patient demonstrates that hyperparathyroidism-induced hypercalcemia may be masked by severe vitamin D deficiency. Prolonged treatment with ergocalciferol after removal of the parathyroid adenoma was necessary to normalize iPTH and replenish vitamin D store.

Osteomalacia in a hemodialysis patient receiving an active vitamin D sterol

BACKGROUND

A 17-year-old Filipino male hemodialysis patient presented for renal transplant evaluation. He had significant skeletal abnormalities characterized by bone pain, an inability to walk, and secondary hyperparathyroidism despite therapy with an active vitamin D sterol (paricalcitol).

INVESTIGATIONS

The patient underwent a physical examination, and his serum levels of calcium, phosphorus, alkaline phosphatase, parathyroid hormone, aluminum and 25-hydroxycholecalciferol (25OH-vitamin D) were determined. X-rays of hips and lower extremities, MRI, and bone histomorphometry after double tetracycline labeling were performed.

DIAGNOSIS

Osteomalacia associated with low 25OH-vitamin D levels.

MANAGEMENT

Monthly therapy with ergocalciferol (vitamin D2) and discontinuation of paricalcitol.

Risk of vitamin A toxicity from candy-like chewable vitamin supplements for children

Numerous vitamin supplements are available over-the-counter to the general public. Some such supplements are available as candy-like chewable preparations to encourage consumption by children. We report 3 cases of overdose of such preparations. Each patient had taken an estimated 200,000 to 300,000 IU of vitamin A. Their circulating vitamin A (retinol and retinyl palmitate) concentrations were monitored over a 6-month period. There were no clinical or biochemical complications noted. However, there were marked increases in both retinol and retinyl palmitate concentrations above age-related reference ranges. In particular, it took 1 to 3 weeks for the serum retinol concentrations to peak and many months for them to normalize. Parents should be warned about the dangers of excessive vitamin consumption. Clinicians should be aware of the late peak in serum retinol concentrations, which may lead to late complications of vitamin A overdose.

All-trans retinoic acid antagonizes the action of calciferol and its active metabolite, 1,25-dihydroxycholecalciferol, in rats

An antagonistic interaction between retinol and calciferol has been established. However, the mechanism by which this antagonism occurs is unclear. One possibility is that retinol affects the metabolism of calciferol. To investigate this hypothesis, retinol- and calciferol-depleted rats were given various amounts of ergocalciferol, cholecalciferol, 1alpha,25-dihydroxycholecalciferol [1,25(OH)2D3], or 24,24-difluoro-1alpha,25-dihydroxycholecalciferol [24-F2-1,25(OH)2D3] in combination with various amounts of retinyl acetate or all-trans retinoic acid (ATRA) in a series of studies. Rats administered 1720 or 3440 microg retinyl acetate once every 3 d for 33 d in combination with 25.8 ng ergocalciferol or 25 ng cholecalciferol every 3 d had lower serum calcium and greater serum phosphorus concentrations than rats fed 0 or 11.4 mug retinyl acetate every 3 d. In addition, rats fed 400 microg ATRA/d in combination with 25.8 ng ergocalciferol every 3 d, 25 ng cholecalciferol every 3 d, 2-5 ng 1,25(OH)2D3/d, or 0.5-1 ng 24-F2-1,25(OH)2D3/d had significantly lower serum calcium and higher serum phosphorus concentrations than rats not given ATRA in the diet. Therefore, both retinyl acetate and ATRA are able to antagonize the action of ergocalciferol and cholecalciferol in vivo. Additionally, ATRA antagonizes the in vivo action of 1,25(OH)2D3 and an analog, 24-F2-1,25(OH)2D3, that cannot be 24-hydroxylated. Together, these results suggest that retinol does not antagonize the action of calciferol by altering the metabolism of calciferol or 1,25(OH)2D3, but does so by another mechanism.

1,24(S)-dihydroxyvitamin D2, an endogenous vitamin D2 metabolite, inhibits growth of breast cancer cells and tumors

BACKGROUND

1,24-Dihydroxyvitamin D2 (1,24(OH)2D2) is a naturally occurring metabolite of vitamin D2 with low calcemic activity and potent antiproliferative activity. We evaluated the activity of 1,24(OH)2D2 in breast cancer models.

MATERIALS AND METHODS

The antiproliferative activity of 1,24(OH)2D2 was quantitated against human and murine breast cancer cell lines. The antitumor activity of 1,24(OH)2D2 was quantitated using MCF-7 xenografts in nude mice.

RESULTS

1,24(OH)2D2 inhibited growth of vitamin D receptor (VDR)-positive, but not VDR-negative, breast cancer cells. 1,24(OH)2D2 (10 microg/kg or 50 microg/kg) reduced MCF-7 xenograft growth by 50% after five weeks. Tumor morphology in treated animals was consistent with replacement of epithelial cells by stromal tissue. Mice treated with 1,24(OH)2D2 showed no loss of body weight, hypercalcemia or kidney calcification.

CONCLUSION

1,24(OH)2D2 inhibits growth of breast cancer cells via VDR-dependent mechanisms; its complete lack of toxicity and significant antitumor activity supports further development for chemotherapeutic applications.