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Table 2 Comparison of total 25(OH)D, free and diplotype-corrected free 25(OH)D, and PTH and DBP concentrations among the GC diplotypes

From: Serum parathyroid hormone is related to genetic variation in vitamin D binding protein with respect to total, free, and bioavailable 25-hydroxyvitamin D in middle-aged Caucasians – a cross-sectional study

GC diplotypes GC1S/1S GC 1S/2 GC 1S/1 F GC 1 F/1 F GC 1 F/2 GC 2/2  
Dependent variable        ANCOVA p-value
S-25(OH)D (nmol/L) 55.9 (280) ± 0.99 51.9 (152) ± 1.34 50.2 (13) ± 4.6 55.1 (38) ± 2.7 58.6 (90) ± 1.7 52.5 (26) ± 3.3 0.033 a
Free 25(OH)D (pmol/L) 12.2 (236) ± 0.29 11.7 (121) ± 0.40 10.1 (10) ± 1.40 11.6 (31) ± 0.80 12.5 (78) ± 0.50 12.6 (24) ± 0.90 0.491a
Diplotype corrected free 25(OH)D (pmol/L)d 14.1 (236) ± 0.30 6.06 (121) ± 0.42 6.40 (10) ± 1.47 9.65 (31) ± 0.85 12.2 (78) ± 0.53 23.1 (24) ± 0.95 <0.001a
Bioavailable 25(OH)D (nmol/L) 4.81 (236) ± 0.12 4.70 (121) ± 0.16 3.97 (10) ± 0.57 4.62 (31) ± 0.33 5.01 (78) ± 0.20 5.07 (24) ± 0.37 0.469a
Diplotype corrected bioavailable 25(OH)D (nmol/L)d 5.60 (235) ± 0.13 2.44 (121) ± 0.17 2.50 (10) ± 0.60 3.86 (31) ± 0.35 4.92 (78) ± 0.22 9.25 (24) ± 0.39 <0.001 a
S-DBP (mg/L) 369 (238) ± 5.55 360 (121) ± 7.78 364 (10) ± 27.1 388(31) ± 15.4 380 (78) ± 9.7 321 (24) ± 17.5 0.039 b
S-PTH (ng/L) 55.0 (289) ± 1.44 56.8 (157) ± 1.96 60.6 (13) ± 6.78 45.6 (38) ± 3.96 57.5 (92) ± 2.55 46.0 (26) ± 4.79 0.040 c
  1. Diplotype means were compared with ANCOVA ± SE. The values are adjusted estimates from ANCOVA. N in parenthesis
  2. Significant p-values are indicated in bold
  3. aAdjusted for age, S-PTH, vitamin D intake, sunlight exposure and sex
  4. bAdjusted for BMI and sex
  5. cS-25(OH)D, Ca intake
  6. GC diplotype was used as a fixed factor
  7. dDiplotype-corrected free and bioavailable 25(OH)D values were calculated by placing a diplotype-specific binding coefficient into the free and bioavailable formulae