Endocrine Abstracts

Introduction: Vitamin D is a hormone essential for calcium absorption and bone mineralization, which is positively associated with bone mineral density. The aim of our study was to evaluate the relationship between 25-OH vitamin D values and parameters of bone mineralization (bone mineral density - BMD) and bone quality (trabecular bone score - TBS) in patients from day to day clinical practice.

Materials and methods: We evaluated 433 postmenopausal women (mean age 61.84±13.62 years) consecutively referred for DXA evaluation in a tertiary endocrinology center. Lumbar BMD was measured using GE Lunar DXA equipment and trabecular bone score (TBS) was evaluated with TBS iNsight software version 3.1.

Results: 17.1% of our patients had a lumbar BMD T Score <−2.5 SD, 48.8% had a T score between −2.49 and −1 SD and the rest of them had a normal BMD T score. Regarding vitamin D status, 160 (37%) patients had normal 25-OH vitamin D levels, 152 (35%) had levels between 20 and 30 ng/ml and the rest (28%) had vitamin D deficiency (less than 20 ng/ml). We found a significant negative correlation between serum 25-OH vitamin D levels and BMI (r=−0.245, P < 0.001), lumbar BMD T score (r=−0.250, P < 0.001) and trabecular bone score (r=−0,109, P < 0.05). Surprisingly, patients with osteoporosis had higher levels of 25-OH vitamin D (30.95±13.7 ng/ml) compared with osteopenic (27.01±11.6 ng/ml) and normal BMD patients (23.65±8.75 ng/ml). However, after controlling for age, BMD and BMI, 25-OH vitamin D levels positively correlated with TBS values (r=0.105, P<0.05).

Conclusions: In daily clinical practice, it is not uncommon to find higher vitamin D levels in osteoporotic patients, probably due to lower BMI and to the higher probability of taking vitamin D supplements. After controlling for age, BMI and BMD, 25-OH vitamin levels were correlated to TBS, a surrogate marker of bone quality.