Serum immunoreactive parathyroid hormone (PTH) is increased in obese as compared with nonobese subjects and declines with weight loss. To

Previous studies demonstrated decreases in serum 25-hydroxyvitamin D in obese subjects. Studies were carried out to determine whiter serum vitamin D is low in obesity. The results indicate that serum vitamin D is significantly lower in obese than in nonobese individuals and may contribute to lower serum 25-hydroxyvitamin D in obesity.

As compared with values in white subjects, bone mass is known to be increased and urinary calcium to be diminished in black individuals. To evaluate the possibility that these changes are associated with alterations in the vitamin Dendocrine system, an investigation was performed in 12 black subjects, 7 men and 5 women, and 14 white subjects, 8 men and 6 women, ranging in age from 20 to 35 yr. All of them were hospitalized on a metabolic ward and were given a constant daily diet containing 400 mg of calcium, 900 mg of phosphorus, and 110 meq of sodium. Whereas mean serum calcium, ionized calcium, and phosphate were the same in the two groups, mean serum immunoreactive parathyroid hormone (350±34 vs. 225±26 pg/ml, P < 0.01) and mean serum 1,25-dihydroxyvitamin D (1,25(OH)2D) (41±3 vs. 29±2 pg/ml, P < 0.01) were significantly higher, and mean serum 25-hydroxyvitamin D (25-OHD) was significantly lower in the blacks than in the whites (6±1 vs. 20±2 ng/ml, P < 0.001). Mean urinary sodium and 24-h creatinine clearance were the same in the two groups, whereas mean urinary calcium was significantly lower (101±14 vs. 166±13 mg/d, P < 0.01) and mean urinary cyclic AMP was significantly higher (3.11±0.47 vs. 1.84±0.25 nM/dl glomerular filtrate, P < 0.01) in the blacks. Further, the blacks excreted an intravenous calcium load, 15 mg/kg body weight, as efficiently as the whites (49±3 vs. 53±3%, NS). Mean serum Gla protein was lower in blacks than in whites (14±2 vs. 24±3 ng/ml, P < 0.02), and increased significantly in both groups in response to 1,25(OH)2D3, 4

OBJECTIVE: Compare effectiveness of maternal vitamin D 3 supplementation with 6400 IU per day alone to maternal and infant supplementation with 400 IU per day.METHODS: Exclusively lactating women living in Charleston, SC, or Rochester, NY, at 4 to 6 weeks postpartum were randomized to either 400, 2400, or 6400 IU vitamin D 3 /day for 6 months. Breastfeeding infants in 400 IU group received oral 400 IU vitamin D 3 /day; infants in 2400 and 6400 IU groups received 0 IU/day (placebo). Vitamin D deficiency was defined as 25-hydroxy-vitamin D (25(OH)D) ,50 nmol/L. 2400 IU group ended in 2009 as greater infant deficiency occurred. Maternal serum vitamin D, 25(OH)D, calcium, and phosphorus concentrations and urinary calcium/creatinine ratios were measured at baseline then monthly, and infant blood parameters were measured at baseline and months 4 and 7.RESULTS: Of the 334 mother-infant pairs in 400 IU and 6400 IU groups at enrollment, 216 (64.7%) were still breastfeeding at visit 1; 148 (44.3%) continued full breastfeeding to 4 months and 95 (28.4%) to 7 months. Vitamin D deficiency in breastfeeding infants was greatly affected by race. Compared with 400 IU vitamin D 3 per day, 6400 IU/day safely and significantly increased maternal vitamin D and 25(OH)D from baseline (P , .0001). Compared with breastfeeding infant 25(OH)D in the 400 IU group receiving supplement, infants in the 6400 IU group whose mothers only received supplement did not differ. CONCLUSIONS:Maternal vitamin D supplementation with 6400 IU/day safely supplies breast milk with adequate vitamin D to satisfy her nursing infant's requirement and offers an alternate strategy to direct infant supplementation. WHAT'S KNOWN ON THIS SUBJECT:The vitamin D concentration in breast milk of women taking 400 IU vitamin D per day is relatively low, leading to vitamin D deficiency in breastfeeding infants. As a result, the American Academy of Pediatrics recommends breastfeeding infant vitamin D supplementation within days after birth. WHAT THIS STUDY ADDS:Maternal vitamin D supplementation alone with 6400 IU/day safely supplies breast milk with adequate vitamin D to satisfy the requirement of her nursing infant and offers an alternate strategy to direct infant supplementation. Dr Hollis, as the principal investigator (PI) of the project, worked with Dr Wagner in the conception of the project, study design, implementation of the study, laboratory analyses, data analyses, and writing of the manuscript; Dr, Wagner as clinical PI of the study, worked with Drs Hollis and Howard, site PI at the University of Rochester (U of R), and all other coinvestigators in the conception of the project, study design, implementation of the study, review of clinical and laboratory data, subject safety, data analyses, and writing of the manuscript; Dr Howard as clinical site PI at the U of R worked directly with Dr Wagner; she was involved in the conception of the project, study design, implementation of the study, laboratory analyses, data analyses, and writing of the manuscript; M...

At physiologic inputs, there is rapid conversion of precursor to product at low vitamin D(3) concentrations and a much slower rate of conversion at higher concentrations. These data suggest that, at typical vitamin D(3) inputs and serum concentrations, there is very little native cholecalciferol in the body, and 25(OH)D constitutes the bulk of vitamin D reserves. However, at supraphysiologic inputs, large quantities of vitamin D(3) are stored as the native compound, presumably in body fat, and are slowly released to be converted to 25(OH)D.

Objective-To determine whether 4000 IU vitamin D 3 /day (vs. 2000 IU/day) during pregnancy is safe and improves maternal/neonatal 25(OH)D in a dose-dependent manner.Study Design-257 pregnant women 12-16 weeks' gestation were enrolled. Randomization to 2000-vs. 4000 IU/day followed one-month run-in at 2000 IU/day. Participants were monitored for hypercalciuria, hypercalcemia and 25(OH)D status.Results-Maternal 25(OH)D (n=161) increased from 22.7(SD 9.7) at baseline to 36.2(SD 15) and 37.9(SD 13.5) in the 2000-and 4000 IU groups, respectively. While maternal 25(OH)D change from baseline did not differ between groups, 25(OH)D monthly increase differed between groups (p<0.01). No supplementation-related adverse events occurred. Mean cord blood 25(OH)D (ng/mL) was 22.1±10.3 in 2000-and 27.0±13.3 in 4000 IU group (p=0.024). After controlling for race and study site, preterm birth and labor were inversely associated with pre-delivery-and mean 25(OH)D, but not baseline 25(OH)D,.Conclusions-Maternal supplementation with 2000 and 4000 IU vitamin D/day during pregnancy improved maternal/neonatal vitamin D status. Evidence of risk reduction in infection, preterm labor and preterm birth was suggestive, requiring additional studies powered for these endpoints.

The incidence of osteoporosis and fractures of the hip are diminished in blacks and in obese subjects. To determine whether bone mass is increased in them, bone mineral density (BMD) of the lumbar spine, trochanter, and femoral neck was measured by dual photon absorptiometry in 89 nonobese white and 51 nonobese black women, all of whom were within 30% of their ideal body weight and between the ages of 20 and 50 yr, and in 21 obese white women and 21 obese black women, all of whom weighed 30% on more than their ideal body weight and were in the same age range. The BMD of the mid radius was also measured by single photon absorptiometry. The mean BMD of the mid radius was higher in black than in white nonobese women [0.73 +/- 0.01 (+/- SE) vs. 0.70 +/- 0.01 g/cm2; P less than 0.01] and was not altered by obesity in either group. The mean BMD was higher in the black than in the white nonobese women at the lumbar spine (1.23 +/- 0.02 vs. 1.16 +/- 0.01 g/cm2; P less than 0.01), trochanter (0.78 +/- 0.02 vs. 0.72 +/- 0.01 g/cm2; P less than 0.01) and femoral neck (0.96 +/- 0.02 vs 0.90 +/- 0.02 g/cm2; P less than 0.02). The mean body weight was higher in the obese than in the nonobese white women (92 +/- 2 vs. 61 +/- 1 kg; P less than 0.001) and black women (94 +/- 3 vs. 63 +/- 1 kg; P less than 0.001). The mean BMD was higher in the obese than in the nonobese white women at the lumbar spine (1.24 +/- 0.03 g/cm2; P less than 0.05), trochanter (0.89 +/- 0.04; P less than 0.001), and femoral neck (0.99 +/- 0.03; P less than 0.01) and was higher in the obese than in the nonobese black women at the lumbar spine (1.33 +/- 0.03 g/cm2; P less tham 0.01), trochanter (0.88 +/- 0.04 g/cm2; P less than 0.05), and femoral neck (1.04 +/- 0.03 g/cm2; P less than 0.05). Multivariate regression analysis revealed positive correlations between body weight and BMD at each of the 3 weight-bearing sites, but not at the mid radius, in both the black women and white women.(ABSTRACT TRUNCATED AT 400 WORDS)

There have been observational reports that maternal vitamin D status at baseline and not closest to delivery is a better predictor of pregnancy outcomes, suggesting that a cascade of events is set into motion that is not modifiable by vitamin D supplementation during later pregnancy. To address this issue, in this exploratory post-hoc analysis using correlation and logistic regression, we sought to measure the strength of the association between serum 25(OH)D concentrations at 3 timepoints during pregnancy: baseline, 1st trimester (<16 wks); 2nd trimester (16-26 wks); and 3rd trimester (≥27 wks) and preterm birth. It was hypothesized that the 25(OH)D value closest to delivery would be most significantly associated with preterm birth. To accomplish this objective, the datasets from NICHD (n=333) and Thrasher Research Fund (n=154) vitamin D supplementation pregnancy studies were combined. The results of this analysis were that 25(OH)D values closer to delivery were more strongly correlated with gestational age at delivery than earlier values: 1st trimester: r=0.11 (p=0.02); 2nd trimester: r=0.08 (p=0.09); and 3rd trimester: r=0.15 (p=0.001). When logistic regression was performed with preterm birth (<37 weeks) as the outcome and 25(OH)D quartiles as the predictor variable, adjusting for study and participant race/ethnicity, as with the correlation analysis, the measurements closer to delivery were more significantly associated and had a higher magnitude of effect. That is, at baseline, those who had serum concentrations <50 nmol/L (20 ng/mL) had 3.3 times of odds of a preterm birth compared to those with serum concentrations ≥100 nmol/L (40 ng/mL; p=0.27). At 2nd trimester, the odds were 2.0 fold (p=0.21) and at the end of pregnancy, the odds were 3.8 fold (p=0.01). The major findings from this exploratory analysis were: (1) maternal vitamin D status closest to delivery date was more significantly associated with preterm birth, suggesting that later intervention as a rescue treatment may positively impact the risk of preterm delivery, and (2) a serum concentration of 100 nmol/L (40 ng/mL) in the 3rd trimester was associated with a 47% reduction in preterm births.