CONTEXT: Osteoporosis and anemia are among the most common diseases in the aging population with an increasing prevalence worldwide.

OBJECTIVE: As the bone-derived hormone fibroblast growth factor 23 (FGF-23) was recently reported to regulate erythropoiesis, we examined age-related associations between hemoglobin levels and bone quality, bone turnover, and FGF-23 concentrations.

DESIGN: We used data from more than 5000 adult subjects who participated in the population-based cohorts of the Study of Health in Pomerania (SHIP and SHIP-Trend). Bone quality was assessed by quantitative ultrasound at the heel, bone turnover by measurement of carboxy-terminal telopeptide of type I collagen (CTX), and intact amino-terminal propeptide of type I procollagen (P1NP) serum concentrations, respectively. Anemia was defined as hemoglobin <13 g/dL in men and <12 g/dL in women. Carboxy-terminal FGF-23 levels were measured in plasma in a subset of 852 subjects.

RESULTS: Anemic subjects had poorer bone quality, higher fracture risk, and lower serum levels of P1NP than nonanemic individuals. Linear regression models revealed positive associations between hemoglobin and bone quality in subjects aged 40 or above and inverse associations with CTX in subjects aged 60 or above. Hemoglobin and FGF-23 concentrations were inversely associated, while FGF-23 was not related to bone quality or turnover.

CONCLUSION: Our data corroborate a close link between FGF-23 and anemia, which is related to poor bone quality in elderly people. We observed no direct association of FGF-23 with bone parameters. Further studies are needed clarifying the role of FGF-23 on bone and red blood cell production.