Low androstenedione/sex hormone binding globulin ratio increases fracture risk in postmenopausal women. The Women's Health in the Lund Area study

Abstract

The Women's Health in the Lund Area (WHILA) project (n=6917) is a cohort study that started in 1995 and includes a postal questionnaire, physical examination, bone density measurement and blood laboratory analyses. Fracture data have been added, and in this report fracture risk and its association with sex hormones was analysed in postmenopausal women without current hormone therapy (HT). A total of 409 women (median age 56.8 years) with 489 fractures were identified from the postmenopausal women without HT during a median follow-up time of 8.4 years. Lower serum levels of androstenedione (p<0.001), testosterone (p=0.008), androstenedione/sex hormone binding globulin (SHBG) ratio (p<0.001), testosterone/SHBG ratio (p=0.003) and higher levels of SHBG (p=0.005) were observed in women with fractures compared to no fracture. No difference in oestradiol levels was observed. Androstenedione and androstenedione/SHBG ratio were further divided into percentiles. Increased fracture risk was found in postmenopausal women with androstenedione in 5th percentile compared to 11-89th percentile HR 1.51 (95% CI 1.02-2.24). The androstenedione/SHBG ratio (11-89th percentile as reference) showed increased fracture risk in women with low ratio 5th percentile HR 1.75 (95% CI 1.20-2.54) and decreased fracture risk with high ratio 95th percentile HR 0.52 (95% CI 0.28-0.98). An increased fracture risk during follow-up was encountered in postmenopausal women with low serum androstenedione and androstenedione/SHBG ratio at baseline and a decreased fracture risk with high androstenedione/SHBG ratio. This study suggests that postmenopausal osteoporosis is influenced by lower levels of androgens.