The Mutual Interplay between Bone, Glucose and Lipid Metabolism: The Role of Vitamin D and PTH

Background: We sought to investigate the mutual interplay between bone, glucose and lipid metabolism in a wide cohort of community-based subjects.

Methods: We studied 1240 blood donors (F/M ratio 1/3.2, mean age 41.9 ± 11.7 SD). Serum ionized (Ca⁺⁺), magnesium (Mg⁺⁺), 25-hydroxy-vitamin D [25(OH)D], PTH-1-84, 1,25-dihydroxyvitamin D [1,25(OH)₂D], total cholesterol (C), HDL-C, triglycerides and glucose were measured and LDL-C levels were calculated in all subjects.

Results: 25(OH)D negatively correlated with BMI (R = -0.11), PTH (R = -0.16) (p < 0.0001), total C (R = -0.06, p < 0.05) and triglycerides (R = -0.13, p < 0.0001) and positively with 1,25(OH)₂D (R = 0.12) and creatinine (R = 0.17) (p < 0.0001). Serum PTH positively correlated with total C (R = 0.08, p < 0.01), LDL-C (R = 0.1, p < 0.001), triglycerides (R = 0.09, p < 0.01) and glucose (R = 0.15, p < 0.0001) and negatively with HDL-C (R = -0.09, p < 0.01). The odds of showing abnormal serum triglycerides and HDL-C increased as 25(OH)D decreased (p < 0.0001 and p < 0.03) and PTH increased (p < 0.03 and p = 0.05), while the odds of showing abnormal LDL-C levels increased in association with elevated PTH (p < 0.01).

Conclusion: Vitamin D, PTH, glucose and lipid metabolism are mutually influenced. Hypovitaminosis D predisposes toward worsening lipid profiles through the actions of PTH, while serum PTH levels per se associate with higher glucose and LDL-C levels.