Endocrine Abstracts

Sufficient vitamin D supply is essential for general health. The total 25-hydoxy-vitamin-D (t-25OHD) level refers to the vitamin D supply and can be measured with various methods. Since these methods are not independent of the serum matrix, differences can be obtained among vitamin D levels measured with different methods. Our aim was to study the vitamin D in healthy blood donors, taking also into consideration the use of oral contraceptives (OC).

Methods: t-25OHD and intact parathormon (PTHi) (ECLIA, cobas e411, Roche) were measured in 131 healthy blood donors (mean age: 33.5±10.5 years; 50 men, 81 women: 41 of them taking OC). Calcium and albumin levels were measured with routine methods (Modular, Roche).

Results: The age of the patients correlated negatively with the t-25OHD (r=−0.29; P<0.01) and albumin (P=−0.33; P<0.001) levels. There was a negative correlation between t-25OHD and PTHi levels (r=−0.26; P<0.01), however, the PTHi was below the upper cut off level. Vitamin D supply was significantly more often insufficient in men (60%) than in women (24%). Only 12% of women taking OC had a poor (50–75 nmol/l) vitamin D supply and there was no lower D vitamin level than 50 nmol/l, while in women not taking OC, the suboptimal (<75 nmol/l) t-25OHD occured three times more often (14/40; 35%; P<0.01). The level of t-25OHD was significantly (P<0.001) higher in women taking OC (101.8±22.9 nmol/l) than in the other group of women (85.6±24.4 nmol/l) or in men (77.9±26.8 nmol/l).

Conclusions: Our results mostly correlate with the literature data; however, the surprisingly good vitamin D supply in women taking OC may suggest the increased production of vitamin D binding globulin in the liver, stimulated by ethynilestradiol.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.