Free 25-(OH)D level may signal misdiagnosed secondary hyperparathyroidism
Click Here to Manage Email Alerts
Free 25-hydroxyvitamin D levels may provide a more accurate vitamin D status than total levels to distinguish normocalcemic primary hyperparathyroidism and secondary hyperparathyroidism, according to findings published in Endocrine Practice.
“Total 25-(OH)D may not be reliable in primary hyperparathyroidism patients, as total 25-(OH) levels are normal but the measured free 25-(OH)D levels are lower in normocalcemic primary hyperparathyroidism subjects than in healthy control subjects,” Xiangbing Wang, MD, PhD, professor of medicine at Robert Wood Johnson Medical School-Rutgers University in New Brunswick, New Jersey, told Healio. “Some normocalcemic primary hyperparathyroidism patients may acutely have secondary hyperparathyroidism based on their lower free 25-(OH)D levels.”
Wang and colleagues assessed free and total serum 25-(OH)D levels in 10 adults with normocalcemic primary hyperparathyroidism (nine women; eight postmenopausal; mean age, 59.9 year; mean BMI, 28.4 kg/m2; serum calcium, 8.6-10.4 mg/dL; total 25-(OH)D 30-40 ng/mL; intact parathyroid hormone 66 pg/mL) and 20 healthy adults matched for age, sex, race and BMI, who served as controls.
Participants in the hyperparathyroidism group had intact parathyroid hormone levels 66 pg/mL to 134 pg/mL vs. 7 pg/mL to 55 pg/mL among controls (P < .001). Mean total 25-(OH)D levels were not statistically significantly different between the hyperparathyroidism group (30-35 ng/mL) and controls (28-38 ng/mL). However, mean free 25-(OH)D levels among the hyperparathyroidism group (5 ± 0.9 pg/mL) were 20% lower vs. controls (6.2 ± 1.3 pg/mL; P = .013). In contrast with total 25-(OH)D, free 25-(OH)D levels were inversely correlated with intact parathyroid hormone levels (r = 0.42; P < .05).
“Importantly, the current findings suggest that total 25-(OH)D levels in normocalcemic primary hyperparathyroidism patients may not be a good indicator of vitamin D status, since there is lower free 25-(OH)D concentration but not lower total 25-(OH)D compared to healthy controls,” the researchers wrote. “We suggest that at least some normocalcemic primary hyperparathyroidism patients have secondary hyperparathyroidism despite normal levels of total 25-(OH)D.”
The researchers acknowledged the small sample size of the study but noted that in an earlier study with 500 participants with primary hyperparathyroidism only one had a normal calcium level.
“Further research in large scale is required to confirm this finding in normocalcemic primary hyperparathyroidism patients from endocrinology clinics,” Wang said. – by Jill Rollet
For more information:
Xiangbing Wang, MD, PhD, can be reached at wangx9@rwjms.rutgers.edu.
Disclosures: The authors report no relevant financial disclosures.
Read more about
Click Here to Manage Email Alerts