LOW BIOAVAILABLE TESTOSTERONE LEVELS PREDICT FUTURE HEIGHT LOSS IN POSTMENOPAUSAL WOMEN

The objective of this study was to examine the relation of endogenous sex hormones to subsequent height loss in postmenopausal women, in who m height loss is usually a surrogate for osteoporotic vertebral fractu res. This was a prospective, community-based study. The site chosen wa s Rancho Bernardo, an upper middle class community in Southern Califor nia. A total of 170 postmenopausal women participated, aged 55-80 year s. None of them were taking exogenous estrogen between 1972 and 1974. Plasma was obtained for sex hormone and sex hormone-binding globulin ( SHBG) assays. Estradiol/SHBG and testosterone/SHBG ratios were used to estimate biologically available hormone levels; bioavailable (non-SHB G-bound) testosterone was measured directly in 60 women. Height loss w as based on height measurements taken 16 years apart. Height loss was strongly correlated with age (p = 0.001). These women lost an average 0.22 cm/year in height. Neither estrone nor estradiol levels were sign ificantly and independently related to height loss. Both estimated bio available testosterone (testosterone/SHBG ratio) and measured bioavail able testosterone levels predicted future height loss (p = 0.02 and 0. 08, respectively) independent of age, obesity, cigarette smoking, alco hol intake, and use of thiazides and estrogen. We conclude that bioava ilable testosterone is an independent predictor of height loss in elde rly postmenopausal women. The reduced height loss is compatible with a direct effect of testosterone on bone mineral density or bone remodel ing.