Bone turnover marker determinants in young women: results from the Safe-D study

Background Bone turnover markers (BTMs) may provide insight into bone health in young women, but have been little studied in this demographic. We aimed to explore the association between body composition, hormonal contraception, bone mineral density and biochemical parameters and BTMs in young women. Methods Participants were community-dwelling females aged 16-25 years, living in Victoria, Australia. Carboxy-terminal cross-linking telopeptide of type 1 collagen (CTX) and total procollagen type 1 N-propeptide (P1NP) were analysed on the Roche Elecsys automated analyzer. A total of 305 were evaluated, after excluding participants with medical conditions or medications (except hormonal contraceptives), which may affect bone metabolism. Results Median (Q1, Q3) BTM values were 540 (410, 690) ng/L for CTX and 61.7 (46.2, 83.7) µg/L for P1NP. Serum CTX and P1NP were inversely associated with chronological age ( P < 0.001), transferrin ( P < 0.020) and serum dehydroepiandrosterone sulphate concentration ( P < 0.001). BTM values were up to 22% lower in combined oral contraceptive (COC) pill users ( P < 0.001). Serum CTX was inversely associated with per cent body fat ( P = 0.009) and tibial cortical volumetric bone mineral density (vBMD; P = 0.003). Serum P1NP concentrations were 23  µg/L higher in participants who reported using an osteopath in the previous year ( P = 0.007). Conclusions These data suggest that BTMs are influenced by age, COC use, body composition, iron status and hormonal profiles. Higher CTX values were associated with lower tibial cortical vBMD. Examining BTMs in relation to interventions aimed at improving bone health in young women is warranted.