Endocrine Abstracts

The majority of circulating total 25-hydroxi-D-vitamin (t-25OHD) is bound to proteins – 90% to vitamin D binding protein (DBP) belonging to the alfa-2-globulin (a-2gl) fraction and 10% to albumin (ALB). Nowadays the t-25OHD level is the most accepted marker of vitamin D supply in physiological states. Our aim was to investigate the t-25OHD concentration in clinical conditions with low albumin levels.

Methods: Seventy-three patients (39 men, 34 women; mean age: 69.3±13.4 years) with low ALB or/and total protein (TP) were studied. 35 patients had chronic renal failure, 8 nephrosis, 19 cirrhosis and 11 malnutrition. The t-25OHD and intact parathormon (PTHi) were determined by ECLIA (Cobas e411, Roche), as well as calcium, TP, ALB were measured, proteinelectrophoresis was estimated (Gelelfo, INTERLAB).

Results: 86% of the cases had vitamin D deficiency (<50 nmol/l), while an optimal vitamin D supply was measured in two cases only. In cases where low ALB (<34 g/l) and low TP (<64 g/l) were present simultaneously (n=52), significantly lower (20.8±17.3 nmol/l) t-25OHD levels were measured than in the patients with low ALB and normal TP levels (n=21; 36.0±26.7 nmol/l). There was a borderline positive correlation (r=0.33) between t-25OHD and TP and a significant (P<0.05) negative correlation between t-25OHD and a-2gl fraction% (r=−0.35). In the group of vitamin D deficient patients (n=45) a pathologically high a-2gl fraction was more frequently observed (71%) than in the group of patients with optimal vitamin D supply (30%).

Conclusions: Our results suggest that in clinical conditions with low ALB and TP levels – especially if hypoproteinemia is associated with an a-2gl excess – t-25OHD levels may not only depend on the vitamin D supply, but also on the presence of its binding proteins and binding capacity besides on increased t-25OHD uptake of cells.

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.