FREE AND BIOAVAILABLE 25-HYDROXYVITAMIN D LEVELS IN PATIENTS WITH PRIMARY HYPERPARATHYROIDISM.
OBJECTIVE
To evaluate free and bioavailable 25-hydroxyvitamin D (25[OH]D) levels in primary hyperparathyroidism (PHPT) patients.


METHODS
Fifty PHPT patients and 50 healthy age-, gender-, and body mass index (BMI)-matched control subjects were enrolled. Levels of 25(OH)D were determined by a radioimmunoassay and vitamin D-binding protein (DBP) were determined by an enzyme-linked immunosorbent assay. Free and bioavailable 25(OH)D were calculated utilizing equations that use average binding coefficients for DBP and albumin.


RESULTS
There was no significant difference in age and BMI between PHPT patients and controls (P>.05). Levels of 25(OH)D, DBP, and DBP-bound 25(OH)D were lower in PHPT patients compared to controls (P<.01). There was no significant difference in free and bioavailable 25(OH)D levels between PHPT patients and controls (P>.05). Levels of intact parathyroid hormone were inversely correlated with free (r = -0.217; P<.05) and bioavailable 25(OH)D levels (r = -0.296; P<.01).


CONCLUSIONS
Serum total 25(OH)D levels were lower, while free and bioavailable 25(OH)D remained similar in patients with PHPT compared to controls. We suggest that low 25(OH)D levels might not reflect true vitamin D nutrition status in PHPT patients.


BACKGROUND
25(OH)D = 25-hydroxyvitamin D BMI = body mass index DBP = vitamin D-binding protein iPTH = intact parathyroid hormone PHPT = primary hyperparathyroidism.
Xiangbing
X
Wang
Sue A
SA
Shapses
Haidar
H
Al-Hraishawi
D000368:Aged; D001682:Biological Availability; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood; D014809:Vitamin D-Binding Protein / Q000097:blood*
D014809:Vitamin D-Binding Protein; D014807:Vitamin D; C104450:25-hydroxyvitamin D