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Objective: To evaluate vitamin D binding protein and free 25-hydroxyvitamin D [25(OH)D] levels in healthy controls compared to primary hyperparathyroidism (PHPT) patients, and to examine PHPT before and after surgery. Methods: Seventy-five PHPT patients and 75 healthy age, gender, and body mass index (BMI) -matched control subjects were examined. In addition, 25 PHPT patients underwent parathyroidectomy and had a 3-month follow up visit. Levels of total and free 25(OH)D, DBP, and intact parathyroid hormone (iPTH) were determined before and 3 months after surgery. Results: There was no significant difference in age and BMI between PHPT patients and controls. Levels of 25(OH)D and DBP were lower in PHPT patients compared to controls ( p < 0.01). There was no significant difference in calculated free and bioavailable 25(OH)D levels between PHPT patients and controls. Calcium and iPTH levels decreased to normal but DBP and DBP-bound-25(OH)D increased ( P < 0.001) after parathyroidectomy. Levels of DBP were inversely correlated with iPTH ( r = −0.406, P < 0.001) and calcium levels ( r = −0.423, P < 0.001). Conclusion: Serum DBP levels were lower in patients with PHPT and parathyroidectomy restored DBP levels. We suggest that lower DBP levels is one of contributing mechanisms of low total 25(OH)D in PTHP patients and the total 25(OH)D levels might not reflect true vitamin D status in PHPT patients.

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(1) Background: This study aimed to investigate the relationship of triglyceride glucose–body mass index (TyG-BMI) with bone mineral density (BMD), femoral neck geometry, and risk of fracture in middle-aged and elderly Chinese individuals. (2) Methods: A total of 832 nondiabetic individuals were selected from the prospective population-based HOPE cohort. All individuals underwent DXA for assessment of BMD at the lumbar spine, femoral neck, and total hip, as well as femoral neck geometry. The 10-year probabilities of both major osteoporotic (MOFs) and hip fractures (HFs) were calculated. (3) Results: Cortical thickness, compression strength index, cross-sectional moment of inertia, cross-sectional area, section modulus, and 25(OH)D levels were significantly lower in women (all p < 0.001). The presence of osteoporosis was related to age, BMI, BMD and femoral neck geometry, TyG-BMI, MOF, and HF. TyG-BMI was positively correlated with BMD. In men, TyG-BMI showed significant negative correlation with HF but not with MOF, the correlation exists only after adjusting for other variables in women. Femoral neck geometries were significantly impaired in individuals with low TyG-BMI. (4) Conclusion: TyG-BMI is positively associated with BMD and geometry, and negatively associated with risk of fracture in nondiabetic middle-aged and elderly Chinese men and women.