Abstract
Aim: In postmenopausal women increased bone turnover is associated with hip fracture apart from bone mineral density. The aim of this study was to evaluate bone metabolism in consideration of vitamin D and hormonal status in elderly female hip fracture patients compared to controls. Material and Methods: Circulating 25-hydroxyvitamin D 3 (25(OH)D), sex hormones, BTM [osteocalcin (OC); propeptide of type-I collagen (PINP); C-terminal telopeptide of type I collagen (CTX-1); tartrate resistant acid phosphatase 5b, (TRAP5b)] and osteoclastogenic cytokines [soluble receptor activator of nuclear factor kB ligand (sRANKL); osteoprotegerin (OPG)] were measured in patients with a low-energy hip fracture and controls without an incident hip fracture (each group n= 47 females). Results: 57.4 % of the patients, but only 10.6. % controls had a severe vitamin D deficiency. T-Score at the lumbar spine was comparable in both groups (-1.8 ± 1.5 vs. -1.6 ± 1.4, p=0.535). In hip fracture patients 25(OH)D (p<0.001), albumin (p<0.001), osteocalcin (OC) (p<0.001) and sRANKL (p<0.001) levels were lower compared to controls, whereas estradiol (p<0.001), cortisol (p<0.001), CTX-1 (p<0.001) and OPG (p<0.001) were higher. Linear regression analysis revealed an independent association between 25(OH)D and CTX-1 in female fracture patients (p=0.023). Higher estradiol levels after hip fracture correlated inversely with OC (p=0.018) and TRAP5b (p=0.004). Multivariable regression analysis demonstrated that 25(OH)D, OC, estradiol (each p<0.001) and albumin (p=0.002) were independently associated with fracture. Higher estradiol levels correlated inversely with OC in fracture patients (p=0.018). Conclusion: 25(OH)D was an independent risk factor of hip fracture and demonstrated an independent association with CTX-1. Unchanged or lower levels of bone formation markers were not associated with 25(OH)D and were partly related to higher of levels estradiol presumably induced by trauma.
Highlights
Hip fractures are considered as the most severe osteoporotic fractures associated with high morbidity and mortality[1,2,3]
Osteoporosis according to a T-score < -2.5 was found in 35.6% of hip fracture patients and 29.8% of controls with no statistical difference (Table 1)
Low levels of 25(OH)D were independently associated with higher levels of the bone resorption marker C-terminal telopeptide of type I collagen TRAP5b (CTX-1) in patients with hip fracture
Summary
Hip fractures are considered as the most severe osteoporotic fractures associated with high morbidity and mortality[1,2,3]. Observational cohort studies revealed that increased bone formation and resorption markers were associated with increased fracture risk[5,6,7]. In postmenopausal women hypogonadism and consecutively lower estrogen levels are associated with increased bone turnover markers (BTM)[8]. Estrogen is a key mediator in bone health. It inhibits bone resorption by direct and indirect actions on osteoclasts and maintains bone formation by reducing osteoblast apoptosis[9]. The decoy receptor OPG is the natural opponent of RANKL displaying anti-resorptive properties[12]. The implication of sRANKL and OPG levels on fracture vulnerability is still discussed controversially[13,14,15,16,17]
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