OR01-6 Delay in Oestrogen Commencement Is Associated with Lower Spine and Hip Bone Mineral Density in Turner Syndrome

Program: Abstracts - Orals, Poster Previews, and Posters
Session: OR01-Osteoporosis: What You Had, What You Lost, and What You Gain
Friday, April 1, 2016: 11:45 AM-1:15 PM
Presentation Start Time: 1:00 PM
Room 157 (BCEC)

Health Disparities
Hanh Nguyen1, Phillip Wong2, Boyd J Strauss3, Peter R Ebeling1, Frances Milat4 and Amanda Vincent*5
1Monash University, Clayton, Australia, 2Hudson Institute of Medical Research, 3Monash University, Clayton VIC, Australia, 4Hudson Institute of Medical Research, Clayton, Australia, 5Monash Health, Clayton, Victoria, Australia
Background: Turner Syndrome (TS) is the most common female chromosomal abnormality, and results from complete or partial X chromosome monosomy. It is associated with short stature, gonadal failure, osteoporosis, and fragility fractures. Chronic estrogen deficiency leading to suboptimal peak bone mass accrual is a major modifiable risk factor for osteoporosis in TS. Pubertal induction with estrogen replacement therapy (ERT) before age 13 is therefore recommended (1).

Aim: To investigate the prevalence and risk factors for low BMD in an established TS cohort.

Method: A retrospective, cross-sectional study of TS patients who underwent DXA scanning at Monash Health, Victoria, Australia from 1998 to 2015. Cases were identified through the hospital Adult TS clinic and Bone Density Department databases. Data from baseline DXA included areal bone mineral density (aBMD) and Z-scores. To adjust for smaller bone size in TS patients, bone mineral apparent density (BMAD) of the lumbar spine (2) and femoral neck (3) was calculated. Low bone mass in young pre-menopausal women was defined as a Z-score < -2.0 (4). Medical history, including ERT and growth hormone therapy (GHT), was collected from medical records. Statistical analysis included descriptive statistics and multivariate regression analysis.

Results: Seventy-nine TS patients were included, and fractures occurred in 30.4% of cases. The median age of TS diagnosis was 11 (range 0-65) years. Primary amenorrhoea was common (81.8%), and the median age of commencing estrogen was delayed at 16 (range 11-46) years. Non-continuous ERT use was reported in 37.9% and GHT was reported in 53%. The median (range) age, height and body mass index was 29 (14-66) years, 148.5 (127.8 – 170.0) cm, and 25.6 (12.4 – 49.5) kg/m2, respectively. The most common osteoporotic risk factor was gonadal failure (89.4%), followed by vitamin D deficiency (40%). Low bone mass in the spine and femoral neck occurred in 26.4% and 7.7%, respectively. Multivariate regression analysis demonstrated that spine and hip aBMD, and BMAD, were inversely associated with age of commencing ERT or years of estrogen deficiency (adjusting for age at DXA and BMI). After adjusting for confounding, GHT was associated with neither aBMD nor BMAD.

Conclusion: Low spinal bone mass is common in TS. Both the delay in commencing estrogen and years of estrogen deficiency are important independent risk factors for reductions in spine and hip bone mass. Avoiding estrogen deficiency is important in optimizing bone health in TS. This depends on early diagnosis of TS to allow age-appropriate pubertal induction and to maximize ERT compliance. Transitional multidisciplinary TS clinics have a role in the early initiation of ERT and in monitoring bone health in TS.

(1) Bondy et al. Clinical Practice Guidelines: Care of Girls and Women with Turner Syndrome: A guidelines of the Turner Syndrome Study Group. JCEM 2007, 92(1):10 –25. (2) Carter et al. New approaches for interpreting projected bone densitometry data. JBMR 1994, 7, 137 –145. (3) Lu et al. Volumetric bone mineral density in normal subjects, aged 5–27 years. JCEM 1996, 81, 1586 –1590. (4) International Society of Densitometry Adult Official Position Paper 2013.

Nothing to Disclose: HN, PW, BJS, PRE, FM, AV

*Please take note of The Endocrine Society's News Embargo Policy at https://www.endocrine.org/news-room/endo-annual-meeting/pr-resources-for-endo