Serum Vitamin D Binding Protein Level Associated with Metabolic Cardiovascular Risk Factors in Women with the Polycystic Ovary Syndrome

Abstract

The objective of the study was to measure the levels of 25-hydroxyvitamin D [25(OH)D] and vitamin D binding protein (VDBP) and assess their relationships with cardiovascular risk factors in women with the polycystic ovary syndrome (PCOS). A group of 267 women, aged 20-35 years (24.7 ± 4.9): 167 with PCOS and 100 healthy women were divided according to body mass index. Biochemical and hormonal parameters were measured. Free and bioavailable 25(OH)D were calculated using the mathematical equations. The percentage of body fat and visceral fat deposit were assessed by DXA. In the normal weight control group total, free, bioavailable 25(OH)D (p<0.001 for all) were significantly higher than in its overweight/obese counterpart, while VDBP levels were comparable. In PCOS women total 25(OH)D (p<0.001), and VDBP (p -0.006) were lower in the overweight/obese subgroups than in the normal weight ones. In both groups serum VDBP levels correlated negatively with serum insulin and positively with sex hormone binding globulin. In PCOS group, in contrast to control group, VDPB was negatively correlated with abdominal fat deposit, BMI, fasting glucose and positively with HDL. Despite lower total 25(OH)D in obese PCOS women, all women with PCOS (lean and obese) had comparable free and bioavailable 25(OH)D, which might be a result of concomitantly lowered serum VDBP levels in obese PCOS women. VDBP might play important role in the regulation of availability of active fractions of 25(OH)D in PCOS women. VDBP seems to be associated with cardiovascular risk factors such as BMI, waist circumference, visceral fat, and fasting serum insulin in women with PCOS.