October 04, 2016
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Total serum 25-(OH)D levels lower in primary hyperparathyroidism vs. healthy adults

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Free and bioavailable 25-hydroxyvitamin D levels are similar among healthy adults and adults with primary hyperparathyroidism, study data show.

However, adults with primary hyperparathyroidism have lower serum total 25-(OH)D levels, according to the researchers.

“The lower 25-(OH)D levels might not reflect true vitamin D status in [primary hyperparathyroidism] as both bioavailable and free 25-(OH)D levels remained relatively stable compared to controls,” Xiangbing Wang, MD, PhD, of the division of endocrinology, metabolism and nutrition at Robert Wood Johnson Medical School, Rutgers University in New Brunswick, New Jersey, told Endocrine Today.

Xiangbing Wang
Xiangbing Wang

Wang and colleagues evaluated 50 adults (mean age, 58.3 years) with primary hyperparathyroidism and 50 healthy age-, gender- and BMI-matched controls (mean age, 58 years) to determine the differences in free and bioavailable 25-(OH)D levels between the groups.

Venous blood samples were collected from participants after a 12-hour overnight fast.

Overall, 36% of participants with primary hyperparathyroidism had 25-(OH)D levels lower than 20 ng/mL. Compared with controls, participants with primary hyperparathyroidism had 20% lower total 25-(OH)D levels and vitamin D-binding protein levels (P < .01). Groups had similar albumin-bound 25-(OH)D levels, whereas controls had higher vitamin D-binding protein bound 25-(OH)D compared with participants with primary hyperparathyroidism (P < .01). Participants with primary hyperparathyroidism had lower albumin levels compared with controls (P < .05).

Inverse correlations were found between serum vitamin D-binding protein levels and levels of intact parathyroid hormone and calcium (P < .01), whereas positive correlations were found between serum vitamin D-binding protein levels and 25-(OH)D (P < .05) and albumin (P < .05).

“Our results suggest that total 25-(OH)D levels might not be an accurate marker of bioactive vitamin D status in [primary parahyperthyroidism] patients,” Wang told Endocrine Today. “Clinicians should be aware of the possibility of worsening the hypercalcemia and hypercalceuira when treating the low total 25-(OH)D level in [primary hyperparathyroidism] patients. Further clinical studies are needed to investigate whether free of bioavailable 25-(OH)D are better markers of 25-(OH)D nutrition status or tissue nutritional status in [primary hyperparathyroidism] patients. Further studies are also needed to investigate the mechanisms of lower vitamin D binding protein and the relationships among [vitamin D binding protein], 25-(OH)D and etiology of primary hyperparathyroidism.” – by Amber Cox

For more information:

Xiangbing Wang, MD, PhD, can be reached at wangx9@rutgers.edu.

Disclosure: The researchers report no relevant financial disclosures.