Establishing a Reference Range for Bone Turnover Markers in Young, Healthy Women

Introduction: Biochemical markers of bone turnover (BTMs) are important in determining fracture risk in postmenopausal women; high levels being associated with increased risk. A proposed goal of anti-resorptive therapy is to reduce BTMs to the lower half of the reference range for healthy young pre-menopausal women. Our aims were a) to establish reference ranges for bone alkaline phosphatase (bone ALP), crosslinked C- and N-telopeptides of type I collagen (betaCTX, NTX), osteocalcin (OC) and procollagen type I N propeptide (PINP) in pre-menopausal women and b) to investigate the determinants of these BTMs.

Methods: BTMs were measured in peripheral blood and second morning void urine collected from 200 healthy pre-menopausal women ages 30 to 45 years. Each subject completed a short medical and lifestyle questionnaire.

Results: BTMs were higher before the age of 35 years than after it. BTMs were higher in women with low BMI (betaCTX and OC), low alcohol consumption (PINP), current smoking habit (bone ALP and NTX), and around time of ovulation (NTX).

Conclusions: We recommend that the age range 35 to 45 years should be used when establishing BTM reference ranges in women.