Endocrine Abstracts

Growing interest in the role of vitamin D in many disease conditions as well as wide availability of vitamin D assays has led to a marked increase in its measurement. Although there are multiple circulating metabolites of vitamin D, those of interest are 25-hydroxyvitamin D2 and D3 and measurements of their relative concentrations is considered helpful. We reviewed vitamin D levels (D2 and D3) obtained on our patient population visiting a large teaching hospital.

Methodology: 12 months data for total 25-hydroxy vitamin D, D2 and D3 levels were obtained from patients seen at our hospital. Vitamin D2 and D3 levels had been performed using LC–MS/MS.

Results: A total of 6246 vitamin D measurements from 5515 patients were analysed over a 12 months period. Total vitamin D levels ranged from 6 to 83 (median: 25 ng/ml), vitamin D2 ranged from <4 to 76 (median: 17 ng/ml) and D3 ranged from 2.1 to 58 (median: 13 ng/ml). Only 47% of patients had optimal vitamin D levels. Among patients with vitamin D deficiency, the majority, 92.1% had un-measurable or low D2 levels compared with 73.9% for D3. D2 levels correlated (r=0.65) better with total vitamin D levels when compared with D3 levels (r=0.51). Few adult patients (n=10) had significant circulating 3-epi-5-OH vitamin D3 levels causing falsely elevated (by 30–79%) total vitamin D levels resulting in a change in vitamin D status from being optimal to exhibiting insufficiency in three patients.

Conclusion: A significant number of patients had suboptimal vitamin D levels. Furthermore, despite dietary fortification, D2 was the most deficient form and was undetectable in a significant number of patients. Measurement of total vitamin D predicted vitamin D status (both D2 and D3). However, measurement of D2 and D3 levels may be needed as second-line investigation and to monitor supplementation.