OR13-6 Hyperparathyroidism and Abdominal Aortic Calcification in Older African American Women: PODA Trial

Background: Abdominal aortic calcification (AAC) detected on lateral vertebral fracture assessment (VFA) images have shown to be independently associated with increased cardiovascular risk and mortality. Vitamin D deficiency and toxicity have also been linked with vascular calcification. Objective: The objective of this study is to determine the natural progression of AAC in older African American (AA) women. We also wanted to evaluate the relationship between bone mineral markers and AAC. Methods: The study of relationship of Physical performance, Osteoporosis prevention with Vitamin D in older African Americans (PODA) is a randomized, double-blind, placebo-controlled 3-year trial examining the effect of vitamin D on bone loss and physical performance in 260 healthy AA women with mean age of 68.2 (65.4-72.5). Serum 25(OH)D levels were maintained above 75 nmol/l in the active group. We studied VFA images and assessed AAC using the Kauppila score(1). The scores were obtained separately for the anterior and posterior walls of L1-4 vertebrae, resulting in a range from 0 to 6 at each vertebral level and 0 to 24 for the total score. We used the antero-posterior severity score (AAC24) to report composite calcification scores and prospectively collected data annually for the PODA study participants over the course of 3 years. AAC24 cut off score of =>5 has shown to be associated with higher (2.4fold) cardiovascular mortality. Results: There were 14.7%(16/109) subjects with presence of AAC (calcification score>0) in the vitamin D group compared to 12.1%(14/116) in the placebo group. Prevalence of extended AAC (AAC24 score>=5) at baseline was 6.4%(7/109) in the vitamin D group and 3.5%(4/116) in the placebo group. At 36 months, the prevalence was 12.7%(9/71) in the vitamin D group and 6.9%(5/73) in the placebo group. The extended calcification scores (AAC24 score >=5) over time were not different in the vitamin D group compared to the placebo group (p-value for time and group interaction was 0.654). We found no association between AAC and serum creatinine, serum calcium, serum 25(OH)D, beta-crosslaps, and bone specific alkaline phosphatase. Interestingly, we found that as PTH increased over time, the odds of calcification (AAC >=5) also increased (p-value for time and PTH interaction was 0.009). Conclusion: Our study showed that a significant positive association exists between PTH and AAC independent of age and treatment group. In contrast to prior observational studies, we found no significant association between vitamin D status and rates of progression of AAC in older AA women. References: 1. Kauppila LI, Polak JF, Cupples LA, Hannan MT, Kiel DP, Wilson PWF(1997) New indices to classify location, severity and progression of calcific lesions in the abdominal aorta: a 25-year follow-up study

Vitamin D Supplementation in Elderly Black Women Does Not Prevent Bone Loss: A Randomized Controlled Trial

Black Americans have lower levels of serum 25(OH)D but superior bone health compared to white Americans. There is controversy over whether they should be screened for vitamin D deficiency and have higher vitamin D requirements than recommended by the Institute of Medicine (IOM). The purpose of this trial was to determine whether Vitamin D supplementation in elderly black women prevents bone loss. A total of 260 healthy black American women, 60 years of age and older were recruited to take part in a two-arm, double-dummy 3-year randomized controlled trial (RCT) of vitamin D₃ versus placebo. The study was conducted in an ambulatory clinical research center. Vitamin D₃ dose was adjusted to maintain serum 25(OH)D above 75 nmol/L. Bone mineral density (BMD) and serum were measured for parathyroid hormone (PTH), C-terminal crosslink telopeptide (CTX), and bone-specific alkaline phosphatase (BSAP) every 6 months. Baseline serum 25(OH)D₃ was 54.8 ± 16.8 nmol/L. There was no group × time interaction effect for any BMD measurement. For all BMD measurements, except for total body and spine, there was a statistically significant negative effect of time (p < 0.001). An equivalency analysis showed that the treatment group was equivalent to the control group. Serum PTH and BSAP declined, with a greater decline of PTH in the treatment group. The rate of bone loss with serum 25(OH)D above 75 nmol/L is comparable to the rate of loss with serum 25(OH)D at the Recommended Dietary Allowance (RDA) of 50 nmol/L. Black Americans should have the same exposure to vitamin D as white Americans. © 2018 American Society for Bone and Mineral Research.

Global prevalence and disease burden of vitamin D deficiency: a roadmap for action in low- and middle-income countries

Vitamin D is an essential nutrient for bone health and may influence the risks of respiratory illness, adverse pregnancy outcomes, and chronic diseases of adulthood. Because many countries have a relatively low supply of foods rich in vitamin D and inadequate exposure to natural ultraviolet B (UVB) radiation from sunlight, an important proportion of the global population is at risk of vitamin D deficiency. There is general agreement that the minimum serum/plasma 25-hydroxyvitamin D concentration (25(OH)D) that protects against vitamin D deficiency-related bone disease is approximately 30 nmol/L; therefore, this threshold is suitable to define vitamin D deficiency in population surveys. However, efforts to assess the vitamin D status of populations in low- and middle-income countries have been hampered by limited availability of population-representative 25(OH)D data, particularly among population subgroups most vulnerable to the skeletal and potential extraskeletal consequences of low vitamin D status, namely exclusively breastfed infants, children, adolescents, pregnant and lactating women, and the elderly. In the absence of 25(OH)D data, identification of communities that would benefit from public health interventions to improve vitamin D status may require proxy indicators of the population risk of vitamin D deficiency, such as the prevalence of rickets or metrics of usual UVB exposure. If a high prevalence of vitamin D deficiency is identified (>20% prevalence of 25(OH)D < 30 nmol/L) or the risk for vitamin D deficiency is determined to be high based on proxy indicators (e.g., prevalence of rickets >1%), food fortification and/or targeted vitamin D supplementation policies can be implemented to reduce the burden of vitamin D deficiency-related conditions in vulnerable populations.

The vitamin D metabolite ratio (VMR) as a predictor of functional biomarkers of bone health

CONTEXT

The vitamin D metabolite ratio (VMR) (serum 24,25(OH)₂ D₃ /25(OH)D₃ ) has been proposed as a biomarker of vitamin D sufficiency to replace serum 25(OH)D.

OBJECTIVE

To examine the relationships of 24,25(OH)₂ D₃ and VMR to functional biomarkers of bone health following vitamin D supplementation.

SETTING

An ambulatory research centre.

DESIGN

Serum from a previous research study of dose response of PTH, calcium absorption and bone turnover to vitamin D supplementation was analysed for vitamin D metabolites (25(OH)D, 24,25(OH)₂ D₃ ).

OUTCOME

The relationship of serum 24,25(OH)₂ D₃ and VMR to calcium absorption, PTH and bone turnover markers was examined.

RESULTS

Although there were strong correlations of serum 25(OH)D with 24,25(OH)₂ D₃ and free 25(OH)D, its correlation with VMR was lower. After vitamin D supplementation, the change in 25(OH)D, 24,25(OH)₂ D₃ and VMR was associated with the change in calcium absorption, PTH and CTX. The correlation of the change in PTH with the change in metabolites was the lowest for VMR. Moreover, estimated dose response for standardized values of vitamin D metabolites showed a beta-coefficient for VMR that was significantly less in magnitude compared to other metabolites.

CONCLUSION

Serum 24,25(OH)₂ D₃ is closely associated with the dose response of serum 25(OH)D to vitamin D supplementation. However, the VMR does not appear to be equivalent to either of these metabolites in its response to increasing vitamin D intake or its association with PTH. It is unlikely that VMR will replace 25(OH)D as a biomarker for vitamin D sufficiency.

ASSOCIATION BETWEEN 25-HYDROXYVITAMIN D AND INTACT PARATHYROID HORMONE LEVELS ACROSS LATITUDE AMONG ADULTS WITH AFRICAN ANCESTRY

OBJECTIVE

To compare levels of 25-hydroxyvitamin D (25[OH]D) associated with a plateauing of intact parathyroid (iPTH) across latitudes among adults with African ancestry.

METHODS

This study included approximately 500 adults of African ancestry ages 25 to 45 years living in 4 sites: Chicago, Illinois (41°N), Jamaica (17°N), Ghana (6°N), and South Africa (34°S). Multivariate linear regression models, a nonlinear logistic growth curve model, and piecewise linear models with a single knot were fitted to estimate the 25[OH]D level associated with a plateauing of iPTH with adjustment for covariates. Goodness of fit was compared using computer intensive permutation tests.

RESULTS

Mean age was 34.7 (SD 6.2) years, and 46.5% were male. Within each site, the percentage of participants with an iPTH level ≥65 pg/mL was higher among females versus males and was most frequent among South African females (17.1%) and lowest among Jamaican males (0.6%). Goodness of fit tests supported linear regression as the preferred model for the association between iPTH and 25[OH]D in the 4 sites with no 25[OH]D level associated with iPTH plateauing in any site. The slope of the association between 25[OH]D and iPTH differed by latitude; it was strongest in the U.S. (β = -0.81; 95% confidence interval [CI] = -1.03, -0.59), and weakest in Jamaica (β = -0.45; 95% CI -0.71, -0.18) with covariate adjustment, but differences in slopes were small.

CONCLUSION

The association between 25[OH]D and iPTH appears linear among adults with African ancestry regardless of latitude within a range of 25[OH]D levels between 10 and 60 ng/mL.

ABBREVIATIONS

BMI = body mass index CI = confidence interval eGFR = estimated glomerular filtration rate iPTH = intact parathryoid hormone 25[OH]D = 25-hydroxyvitamin D.

Free 25(OH)D and Calcium Absorption, PTH, and Markers of Bone Turnover

CONTEXT

It has been proposed that serum free 25-hydroxyvitamin D [25(OH)D] may better reflect vitamin D action than total 25(OH)D. An ELISA for serum free 25(OH)D has recently become available, permitting direct assay.

OBJECTIVE

To determine whether serum free 25(OH)D provides additional information in relation to calcium absorption and other biomarkers of vitamin D action compared to total serum 25(OH)D.

SETTING

Ambulatory research setting in a teaching hospital.

OUTCOME

Serum free 25(OH)D measured in a previously performed study of varied doses of vitamin D3 (placebo and 800, 2000, and 4000 IU) on calcium absorption, PTH, procollagen type 1 N-terminal propeptide, and C-terminal telopeptides of type I collagen. Free 25(OH)D was measured by ELISA. Calcium absorption was measured at baseline and at 10 weeks using stable dual calcium isotopes.

RESULTS

Seventy-one subjects completed this randomized, placebo-controlled trial. Baseline group mean free and total 25(OH)D varied from 4.7 ± 1.8 to 5.4 ± 1.5 pg/mL, and from 23.7 ± 5.9 to 25.9 ± 6.1 ng/mL, respectively. Participants assigned to the 4000-IU dose arm achieved free 25(OH)D levels of 10.4 pg/mL and total 25(OH)D levels of 40.4 ng/mL. Total and free 25(OH)D were highly correlated at baseline and after increasing vitamin D dosing (r = 0.80 and 0.85, respectively). Free 25(OH)D closely reflected changes in total 25(OH)D. PTH was similarly correlated at baseline and follow-up with total and free 25(OH)D. Serum C-terminal telopeptides of type I collagen had a moderate positive correlation with total and free 25(OH)D at follow-up. The serum 1,25-dihydroxyvitamin D change increased significantly with the change in 25(OH)D but not with the change in free 25(OH)D.

CONCLUSION

There was no advantage from measuring free over total 25(OH)D in assessing the response of calcium absorption, PTH, and markers of bone turnover to vitamin D. Free 25(OH)D responded to increasing doses of vitamin D in a similar fashion to total 25(OH)D.

Free 25(OH)D and the Vitamin D Paradox in African Americans

CONTEXT

African Americans have a lower total serum 25-hydroxyvitamin D [25(OH)D] but superior bone health. This has been referred to as a paradox. A recent publication found that free serum 25(OH)D is the same in black and white individuals. However, the study was criticized because an indirect method was used to measure free 25(OH)D. A direct method has recently been developed.

OBJECTIVE

We hypothesized that although total serum 25(OH)D is lower in African Americans, free serum 25(OH)D measured directly would not differ between races.

DESIGN

White and black healthy postmenopausal women were matched for age and body mass index. Serum total 25(OH)D, PTH, 1,25-dihydroxyvitamin D, vitamin D binding protein (VDBP), and bone density were measured. Measurement of free 25(OH)D was carried out using an ELISA.

SETTING

The study was conducted at an ambulatory research unit in a teaching hospital.

OUTCOME

A cross-racial comparison of serum free 25(OH)D was performed.

RESULTS

A propensity match resulted in the selection of a total of 164 women. Total 25(OH)D was lower in black women (19.5 ± 4.7 vs 26.9 ± 6.4 ng/mL), but a direct measurement of free 25(OH)D revealed almost identical values (5.25 ± 1.2 vs 5.25 ± 1.3 ng/mL) between races. VDBP was significantly lower in blacks when using a monoclonal-based ELISA but higher with a polyclonal-based ELISA. Serum PTH, 1,25-dihydroxyvitamin D, and bone density were higher in African Americans.

CONCLUSIONS

Free serum 25(OH)D is the same across races despite the lower total serum 25(OH)D in black women. Results comparing VDBP between races using a monoclonal vs a polyclonal assay were discordant.

25-Hydroxyvitamin D in African-origin populations at varying latitudes challenges the construct of a physiologic norm

BACKGROUND

The vitamin D-endocrine system is thought to play a role in physiologic processes that range from mineral metabolism to immune function. Serum 25-hydroxyvitamin D [25(OH)D] is the accepted biomarker for vitamin D status. Skin color is a key determinant of circulating 25(OH)D concentrations, and genes responsible for melanin content have been shown to be under strong evolutionary selection in populations living in temperate zones. Little is known about the effect of latitude on mean concentrations of 25(OH)D in dark-skinned populations.

OBJECTIVE

The objective was to describe the distribution of 25(OH)D and its subcomponents in 5 population samples of African origin from the United States, Jamaica, Ghana, South Africa, and the Seychelles.

DESIGN

Participants were drawn from the Modeling of the Epidemiologic Transition Study, a cross-sectional observational study in 2500 adults, ages 25-45 y, enrolled between January 2010 and December 2011. Five hundred participants, ∼50% of whom were female, were enrolled in each of 5 study sites: Chicago, IL (latitude: 41°N); Kingston, Jamaica (17°N); Kumasi, Ghana (6°N); Victoria, Seychelles (4°S); and Cape Town, South Africa (34°S). All participants had an ancestry primarily of African origin; participants from the Seychelles trace their history to East Africa.

RESULTS

A negative correlation between 25(OH)D and distance from the equator was observed across population samples. The frequency distribution of 25(OH)D in Ghana was almost perfectly normal (Gaussian), with progressively lower means and increasing skewness observed at higher latitudes.

CONCLUSIONS

It is widely assumed that lighter skin color in populations outside the tropics resulted from positive selection, driven in part by the relation between sun exposure, skin melanin content, and 25(OH)D production. Our findings show that robust compensatory mechanisms exist that create tolerance for wide variation in circulating concentrations of 25(OH)D across populations, suggesting a more complex evolutionary relation between skin color and the vitamin D pathway.

The vitamin D analogue 2MD increases bone turnover but not BMD in postmenopausal women with osteopenia: results of a 1-year phase 2 double-blind, placebo-controlled, randomized clinical trial

Most osteoporosis drugs act by inhibiting bone resorption. A need exists for osteoporosis therapies that stimulate new bone formation. 2-Methylene-19-nor-(20S)-1α,25-dihydroxyvitamin D(3) (2MD) is a vitamin D analogue that potently stimulates bone formation activity in vitro and in the ovariectomized rat model. In this randomized, double-blind, placebo-controlled study of osteopenic women, the effect of daily oral treatment with 2MD on bone mineral density (BMD), serum markers of bone turnover, and safety were assessed over 1 year. Volunteers were randomly assigned to three treatment groups: placebo (n = 50), 220 ng of 2MD (n = 54), and 440 ng of 2MD (n = 53). In general, 2MD was well tolerated. Although 2MD caused a marked increase in markers of bone formation, it did not significantly increase BMD. Since 2MD also shows marked activity on bone resorption (as revealed by dose-dependent increases in serum C-telopeptide cross-links of type I collagen in this study), 2MD likely stimulated both bone formation and bone resorption, thereby increasing bone remodeling.

The relative influence of calcium intake and vitamin D status on serum parathyroid hormone and bone turnover biomarkers in a double-blind, placebo-controlled parallel group, longitudinal factorial design

BACKGROUND

Adequate calcium and vitamin D are needed to maintain calcium balance.

OBJECTIVE

Our objective was to examine the influence of calcium intake and vitamin D exposure separately and their interaction on biomarkers of calcium sufficiency.

DESIGN

Healthy men and women, age 20-80 yr, were randomly allocated to four groups: 1) double placebo, 2) calcium (1200 mg daily) plus placebo, 3) vitamin D(3) (100 microg) plus placebo, and 4) vitamin D(3) and calcium. Fasting serum and urine as well as serum and urine 2 h after a calcium load (600 mg of calcium carbonate) were obtained at baseline and 3 months.

RESULTS

Ninety-nine participants were randomized; 78 completed the study. Baseline demographics, protein intake and laboratory studies did not differ among the four groups. Study medication compliance was 90%. Fasting bone turnover markers declined after 3 months only in the two groups given calcium supplements and increased in the vitamin D(3) plus placebo calcium group. The calcium load resulted in a decrease in PTH and in bone turnover markers that did not differ among groups. Urinary calcium excretion increased in the combined group. Mean serum 25-hydroxyvitamin D increased from a baseline of 67 (18 sd) nmol/liter to 111 (30 sd) nmol/liter after vitamin D supplementation.

CONCLUSION

Increased habitual calcium intake lowered markers of bone turnover. Acute ingestion of a calcium load lowered PTH and bone turnover markers. Additional intake of 100 microg/d vitamin D(3) did not lower PTH or markers of bone turnover.

Effect of inhaled corticosteroid on bone density in asthmatic patients: a pilot study

We investigated the effect of long-term inhaled (ICS) and oral corticosteroid (OCS) therapy on bone density by using single and dual photon absorptiometry. We studied a group of five asthmatic patients who inhaled an average of 326 micrograms/day of beclomethasone dipropionate equivalents for 50 months (range 36 to 62 months) and a control group of five asthmatic patients on OCS, who used 12.5 mg of prednisone equivalents daily for an average of 57 months (range 22 to 120 months). The ICS group's average bone densities relative to age and sex-matched controls were 99.7%, 99.2%, and 90.0% for the radius, spine, and hip, respectively. The OCS group's average bone densities relative to age-matched and sex-matched controls were 94.4%, 85.4%, and 84.5% for the identical sites. A dose-response relationship between the cumulative dose of ICS and the relative bone density was absent in the study group but demonstrable in the control group of asthmatics on long-term OCS therapy. These results suggest that ICS therapy, unlike OCS, may not induce bone loss at the doses used by our subjects. Further research is required to determine whether a single user of ICS with unusually low bone density measurements represents a biologic variant, or a subgroup of patients who are especially sensitive to the systemic effects of ICS.

Parathyroid function in acromegaly

Parathyroid function was assessed in six acromegalic subjects by measurement of serum levels of parathyroid hormone (PTH). Only one patient had increased PTH levels. These findings suggest that hyperparathyroidism does not uniformly occur in acromegaly.