Effect of transdermal vs.oral estrogen therapy on achieving near final adult height and near peak bone mass in growth hormone treated adolescents with Turner syndrome Sevket Yigit M.D Connecticut Children’s Medical Center Endocrinology and Diabetes

ABSTRACT Estrogen replacement in Turner Syndrome (TS) is accomplished most commonly using oral estrogen preparations. Based on preliminary data we hypothesize that transdermal vs oral estradiol will have more favorable effect on near final adult height (FAH) and near peak bone mass (PBM) in growth hormone (GH) treated adolescents with TS. The aim of the study is to evaluate the effect of transdermal vs. oral estrogen on growth and bone mass and their correlation with growth factor levels, markers of bone turnover and sex steroid levels. This 2 year selectively randomized prospective study involves two treatment groups: equivalent doses of oral vs. transdermal estradiol in combination with standard growth hormone therapy. The TS adolescents ages years will be selectively randomized to each group by bone age. Estrogen dose will be gradually increased every 6 months over the two years in both groups mimicking normal puberty. With a sample size of 12 in each group and test significance level of 0.05, we will have 80 % power to detect a 25 % difference in growth of two groups. There is no preliminary data in terms of bone mass to evaluate sample size estimation for significant difference between two groups. Analysis of outcomes will be done between study groups as well as within each study group over time. t

GONADAL DYSGENESIS CHRONIC ESTROGEN DEFICIENCY

Background Individuals with Turner Syndrome (TS) are estrogen deficient during their pubertal and postpubertal years. Estrogen therapy is needed during adolescence not only to provide adequate feminization but may play a role in maximizing near final adult height (FAH) and near peak bone mass (PBM) if administered more physiologically in combination with growth hormone (GH) therapy. ESTROGEN THERAPY IN TSESTROGEN THERAPY IN TS Low dose stimulates linear growth. High dose inhibits growth. Ideally it has to augment growth, should not prematurely induce epiphysial fusion and should enhance FAH and PBM. Estrogen therapy in TS should mimic normal puberty.

TYPES OF ESTROGEN TREATMENT:TYPES OF ESTROGEN TREATMENT: Oral vs. transdermal ( systemic) Oral estrogen… first pass effect through the liver Transdermal…provides constant serum levels similar to ovarian estradiol secretion

Hypotheses Transdermal versus oral estradiol will have a more favorable effect on linear growth and near FAH in GH treated TS adolescents. Transdermal versus oral estradiol will also have a more favorable effect on bone mass accrual and near PBM in GH treated TS adolescents.

Preliminary Studies A number of investigators have studied the interplay between exogenous estrogen and the GH- IGF-1 axis in adult females. Hypogonadal women with transdermal estradiol require lower doses of GH than those on oral estrogen. RoelfsenaRoelfsena observed that a switch from equivalent doses of oral to transdermal estradiol increased IGF-1 levels significantly in 20 adult women with LH and GH deficiency suggesting increased effectiveness of GH therapy when receiving transdermal as compared to oral estrogen(1).

HoHo reports increased GH but decreased IGF-1 levels in oral estrogen treated postmenopausal women presumed to result from the direct inhibitory effect of high estradiol concentration on hepatic IGF-1 production. In a subsequent study, Ho observed enhanced IGF-1 production and evidence of increased osteoblastic bone formation in transdermal estrogen treated postmenopausal women (2,3). RosenfieldRosenfield studied the effect on growth of systemic estrogen as compared to oral estrogen in combination with GH therapy. They compared I.M. depot estradiol initiated at low doses and increased gradually every 6 months over 2 years with routine oral estrogen therapy. Gain in near FAH at 2 years was 2.6 cm greater in depot estradiol vs routine estradiol group ( p<.001)(4).

Recent epidemiological studies in Denmark reported a significantly increased prevalence of symptomatic osteoporosis with fractures at all ages in TS but which increases substantially during later adulthood(5). Lanes studied young TS women (mean age 18.2 years) with previously normal bone density at the time GH therapy was discontinued and observed decreased bone mass several years later despite continuous oral estrogen therapy(6). Onyirimba and RubinAt our institution, Onyirimba and Rubin compared the effect of transdermal vs. oral estrogen therapy in 15 TS young adults ( mean age 21.6 years) on bone turnover and its correlation with growth factors and gonadal steroid levels. They observed a relative preservation of IGF-1 and a significant decrease in IGFBP-3 in the transdermal as compared to oral estradiol group which was associated with a net increase in markers of bone formation (7).

Collectively, the preliminary data supports the use of low dose systemic estradiol for initiation of estrogen therapy in GH treated TS young adolescents with gradual increments over a several year period. This more physiological treatment approach has greater potential to promote both FAH and PBM in a group of individuals with limited genetic potential for both.Collectively, the preliminary data supports the use of low dose systemic estradiol for initiation of estrogen therapy in GH treated TS young adolescents with gradual increments over a several year period. This more physiological treatment approach has greater potential to promote both FAH and PBM in a group of individuals with limited genetic potential for both.

Specific Aims To measure increments in growth and near FAH in GH treated TS adolescents on transdermal vs oral estradiol. To measure increments in bone mineral density and near PBM in a group of GH treated TS adolescents on transdermal vs oral estradiol. To correlate the changes in growth and bone mineral density with changes in growth factor levels, markers of bone turnover, and pubertal hormones

Inclusion criteria 1. TS girls ages 12 to15 years. 2. On standard GH treatment for 2 years or more 3. No previous estrogen therapy or on low dose estrogen therapy for less than or equal to one year with a wash-out period of three months prior to study entry. 4. TS girls with adequately treated hypothyroidism

Exclusion Criteria 1. Underlying chronic disease or use of medications known to interfere with bone metabolism ( ie. anticonvulsants, glucocorticoids) 2. Patients with major contraindications for estrogen therapy (Patients with hypercoagulability, and severe liver disease by history are excluded) 3. History of fracture or immobilization in the last one year. 4. Mosaic TS patients with spontaneous puberty. 5. Mosaic TS patients with sufficient estradiol levels. 6. Pregnancy

Selectively randomized prospective study Group 1 Turner Syndrome ( years old) Group 2 Turner Syndrome (12-15 years old) Bone Age Matched INITIAL EVALUATION TRANSDERMAL ESTRADIOLORAL ESTRADIOL mg for 6 months mg for 6 months mg for 6 months 0.05 mg for 6 months 0.25 mg for 6 months 0.5 mg for 6 months 0.75 mg for 6 months 1 mg for 6 months Evaluations every 6 months FINAL EVALUATION Sample size: 12 for each group

Outcome Measures Height,height velocity Bone age Growth factors (IGF-1, IGFBP-3) Bone turnover markers (BS-ALP, osteocalcin, PINP, N-telopeptides) Bone mineral density ( yearly) Pubertal hormones (estradiol, estrone, SHBG, LH, FSH, total and free testosterone, DHT, DHEA-S).

Significance –Recent observations suggest possible advantages of systemic vs. oral estrogen therapy on FAH and PBM in TS. Considering the fact that on average, 15% of FAH and 40% of PBM are achieved during puberty, adolescents with TS may benefit from transdermal vs oral estrogen therapy with regard to FAH and PBM. Since a relatively small increment in bone mass can result in a significant decrease in fracture risk later on, use of transdermal vs oral estrogen may decrease the risk of developing symptomatic osteoporosis in TS. Long term transdermal estrogen therapy may result in long term benefits in this population.

WORK IN PROGRESS Grant supports: GCRC University of Connecticut, Endocrine Fellows Foundation, Eli-Lilly Company Recruitment of subjects is in progress currently. There is no preliminary data available.

References 1)Roelfsema, F, Janssen Y., A switch from oral (2mg/day) to transdermal ( 50 mcg/day) 17-beta estradiol therapy increases serum IGF-1 levels in recombinant GH substituted women with GH deficiency. J. of Clin.Endoc.and Metab.2000;85(1): )Ho K.Y, Lazarus L., Contrasting effects of oral and transdermal routes of estrogen replacement therapy on 24 hour growth hormone (GH) secretion, IGF-1 and GH binding protein in ostmenopausal women. J. of Clin.Endoc. and Metab.1991; 72 (2): )Ho K.Y, Weissberger A.J, Impact of short term estrogen administration on growth hormone secretion and action: Distinct route dependent effects on connective tissue and bone tissue metabolism. J. of Bone and Mineral Research.1992; 7(7): )Rosenfield R. Optimizing estrogen replacement treatment in Turner Syndrome. Pediatrics 1998; 102: )Gravholt CH. Morbidity in Turner Syndrome. J. Clin. Epidemiol 1998;51(2): )Lanes R Decreased bone mass despite long term estrogen replacement therapy in young women with Turner’s Syndrome and previously normal bone density. Fertil. Steril-1999 Nov; 72(5)-896 7)Onyirimba M, Rubin K. Effect of Transdermal vs. Oral estradiol on growth factors and markers of bone turnover in young adults with TS.( Manuscript in preparation)