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

Table 3 Comparison of 25(OH)D, free- and diplotype-corrected free 25(OH)D, and DBP and PTH concentrations among the GC haplotypes

GC haplotype	GC1S			GC1F			GC2			ANCOVA p-value
Dependent variable
S-25(OH)D (nmol/L)	57.1 (281)	±	1.04	50.6 (13)	±	4.9	52.7 (25)	±	3.53	0.231^a
Free 25(OH)D (pmol/L)	12.5 (237)	±	0.30	10.1 (10)	±	1.46	12.6 (23)	±	0.97	0.280^a
Diplotype corrected free 25(OH)D (pmol/L)^e	14.2 (237)	±	0.35	6.30 (10)	±	1.70	22.8 (23)	±	1.12	<0.001 ^a
Bioavailable 25(OH)D (nmol/L)	4.92 (237)	±	0.12	3.98 (10)	±	0.59	5.01 (23)	±	0.39	0.261^a
Diplotype corrected bioavailable 25(OH)D (nmol/L)^e	5.61 (237)	±	0.14	2.47 (10)	±	0.68	9.15 (23)	±	0.45	<0.001 ^a
S-DBP (mg/L)	369 (240)	±	5.60	364 (10)	±	27.4	320 (23)	±	18.1	0.039 ^b
S-PTH (ng/L)	54.5 (283)	±	1.39	60.7 (13)	±	6.52	44.7 (25)	±	4.70	0.078c^d

Haplotype means were compared with ANCOVA ± SE. The values are adjusted estimates from ANCOVA. N in parenthesis
Significant p-values are indicated in bold
^aAdjusted for age, S-PTH, vitamin D intake, sunlight exposure and sex
^bAdjusted for BMI and sex
^cS-25(OH)D, Ca intake
^da linear trend, p = 0.044
GC haplotype was used as a fixed factor
^eHaplotype-corrected free and bioavailable 25(OH)D values were calculated by placing a haplotype-specific binding coefficient into the free and bioavailable formulae

ISSN: 2055-0928