L Meng1, C Su2, S A Shapses1, X Wang3. 1. Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ, 08901, USA. 2. Graduate School of Biomedical Science, Rutgers University, Piscataway, NJ, 08854, USA. 3. Division of Endocrinology, Department of Medicine, Rutgers University-Robert Wood Johnson Medical School, New Brunswick, NJ, 08093, USA. wangx9@rwjms.rutgers.edu.
Abstract
PURPOSE: To evaluate total and free vitamin D metabolites and hormone-to-prohormone [1,25(OH)2D/25(OH)D] "activation ratio" in PHPT patients with low or insufficient vitamin D status. METHODS: Thirty female patients with primary hyperparathyroidism (PHPT) and 30 age and body mass index (BMI) matched healthy controls were enrolled. Serum levels of calcium, intact parathyroid hormone (iPTH), vitamin D binding protein (DBP), albumin, total 25(OH)D and 1,25(OH)2D were measured. The activation ratio of vitamin D was calculated as total 1,25(OH)2D/25(OH)D. Calculated serum-free 25(OH)D and 1,25(OH)2D levels were also reported. RESULTS: Compared to the control subject, patients with PHPT had a lower total 25(OH)D and DBP levels (p < 0.001). The serum concentration of free 25(OH)D and total 1,25(OH)2D were similar between the two groups; but free 1,25(OH)2D levels were about 26% higher in the PHPT patients compared to controls (p < 0.001). PHPT patients had a significantly higher activation ratio (p < 0.01), although their total 25(OH)D were lower than controls. The free (but not total) 1,25(OH)2D level was inversely correlated with DBP (p < 0.01). Both free 1,25(OH)2D levels and activation ratio were positively correlated with iPTH and calcium levels (p < 0.01). The activation ratio was highly correlated with levels of total vitamin D stores and free vitamin D metabolites (p < 0.001). CONCLUSION: Patients with PHPT had significantly higher free 1,25(OH)2D levels and activation ratio compared to control subjects. We suggest that levels of free vitamin D metabolites and vitamin D activation ratio may provide additional values for the diagnosis and therapeutic choices in these patient populations with compromised vitamin D status.
PURPOSE: To evaluate total and free vitamin D metabolites and hormone-to-prohormone [1,25(OH)2D/25(OH)D] "activation ratio" in PHPT patients with low or insufficient vitamin D status. METHODS: Thirty female patients with primary hyperparathyroidism (PHPT) and 30 age and body mass index (BMI) matched healthy controls were enrolled. Serum levels of calcium, intact parathyroid hormone (iPTH), vitamin D binding protein (DBP), albumin, total 25(OH)D and 1,25(OH)2D were measured. The activation ratio of vitamin D was calculated as total 1,25(OH)2D/25(OH)D. Calculated serum-free 25(OH)D and 1,25(OH)2D levels were also reported. RESULTS: Compared to the control subject, patients with PHPT had a lower total 25(OH)D and DBP levels (p < 0.001). The serum concentration of free 25(OH)D and total 1,25(OH)2D were similar between the two groups; but free 1,25(OH)2D levels were about 26% higher in the PHPT patients compared to controls (p < 0.001). PHPT patients had a significantly higher activation ratio (p < 0.01), although their total 25(OH)D were lower than controls. The free (but not total) 1,25(OH)2D level was inversely correlated with DBP (p < 0.01). Both free 1,25(OH)2D levels and activation ratio were positively correlated with iPTH and calcium levels (p < 0.01). The activation ratio was highly correlated with levels of total vitamin D stores and free vitamin D metabolites (p < 0.001). CONCLUSION: Patients with PHPT had significantly higher free 1,25(OH)2D levels and activation ratio compared to control subjects. We suggest that levels of free vitamin D metabolites and vitamin D activation ratio may provide additional values for the diagnosis and therapeutic choices in these patient populations with compromised vitamin D status.
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