ABSTRACT
Transgender youth with gender dysphoria are often treated with a gonadotropin-releasing hormone (GnRH)
agonist to suppress sex steroids and pubertal development. However, there is little information available on its
effects on bone health in young peri-pubertal transgender youth. Sex steroid suppression can alter
mesenchymal stem cells to differentiate preferentially into adipocytes over osteoblasts, compromising
osteogenesis, bone formation, and bone density in both adolescents and adults. The current investigators have
previously demonstrated that adolescents with restrictive eating disorders and hypoestrogenism experience
bone marrow shifts from red (hematopoietic) to yellow (fatty) marrow with progression of disease. These bone
marrow changes may have adverse long-term implications for bone formation, bone accretion during
adolescence, and ultimately, lifetime skeletal health. Examining how bone marrow composition is altered after
pubertal blockade in transgender youth, and its relation to bone density, structure, and cross-sectional
geometry, could provide a mechanistic understanding of the effects of a GnRH agonist on a young, immature
skeleton. This proposal will examine the skeletal effects of pubertal blockade, the initial phase of transgender
medical management, prior to gender affirming hormonal therapy (estrogen or testosterone therapy). The
study will provide new insights on bone health in transgender youth, examining bone marrow composition via
magnetic resonance imaging (MRI) and spectroscopy (MRS). These results will be correlated with BMD
measurements obtained by the clinical assessment tool, dual-energy x-ray absorptiometry (DXA), and the
research tool, peripheral quantitative computed tomography (pQCT). We will also address the clinically
relevant question of how bone marrow composition relates to bone density and skeletal strength in young
adolescents who are undergoing pubertal blockade. We will recruit a cohort of adolescents including those
assigned female at birth (AFAB) and assigned male at birth (AMAB), and matched healthy controls, and
examine bone marrow composition (by MRI/MRS), bone density (by DXA + pQCT), and bone structure and
cross-sectional geometry (by pQCT), before and after 12 months of pubertal blockade. This project will
leverage our large patient population as a two-site study in nationally recognized pediatric hospitals and our
extensive experience with DXA, pQCT, and MRI/MRS. In an exploratory aim, we will also consider the effect of
pubertal blockade on anxiety, depression, and health-related quality of life. Findings from the proposed study
will allow us to identify preventive strategies to counter potential long-term adverse sequelae of pubertal
blockade such as early osteoporosis and fractures, raise awareness for providers of transgender youth, and
help guide monitoring after receipt of a GnRH agonist.