Effects of hypogonadism on brain development during adolescence in girls with Turner syndrome

Abstract

Gonadal steroids play an important role in brain development, particularly during puberty. Girls with Turner syndrome (TS), a genetic disorder characterized by the absence of all or part of the second X chromosome, mostly present a loss of ovarian function and estrogen deficiency, as well as neuroanatomical abnormalities. However, few studies have attempted to isolate the indirect effects of hormones from the direct genetic effects of X chromosome insufficiency. Brain structural (i.e., gray matter [GM] morphology and white matter [WM] connectivity) and functional phenotypes (i.e., resting-state functional measures) were investigated in 23 adolescent girls with TS using multimodal MRI to assess the role of hypogonadism in brain development in TS. Specifically, all girls with TS were divided into a hormonally subnormal group and an abnormal subgroup according to their serum follicle-stimulating hormone (FSH) levels, with the karyotypes approximately matched between the two groups. Statistical analyses revealed significant effects of the "group-by-age" interaction on GM volume around the left medial orbitofrontal cortex and WM diffusion parameters around the bilateral corticospinal tract, anterior thalamic radiation, left superior longitudinal fasciculus, and cingulum bundle, but no significant "group-by-age" or group differences were observed in resting-state functional measures. Based on these findings, estrogen deficiency has a nontrivial impact on the development of the brain structure during adolescence in girls with TS. Our present study provides novel insights into the mechanism by which hypogonadism influences brain development during adolescence in girls with TS, and highlights the important role of estrogen replacement therapy in treating TS.

Keywords: Turner syndrome; brain structural imaging; diffusion tensor imaging; gray matter volume; hypogonadism; the X chromosome; white matter connectivity.

Figure 1

Significant effects of the interaction between age and group (abnormal group/subnormal group) on GMV. The GM cluster showing significant effects of the “group‐by‐age” interaction (FWE‐corrected p‐value <.05). The scatter plot on the right depicts the effects of the interaction between age and group on cluster‐averaged GMV values for the significant cluster shown on the left. GMV, gray matter volume; FWE, family‐wise error [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 2

Significant effects of the interaction between age and group (abnormal group/subnormal group) on diffusion metrics. (a) One significant cluster for axial diffusivity (AD). (b–d) three significant clusters for radial diffusivity (RD). All clusters were considered significant if the FWE‐corrected p‐value was <.05 at the cluster level. The scatter plots shown in the right panels depict the effects of the interaction between age and group on cluster‐averaged AD and RD values for these four clusters. FWE, family‐wise error [Color figure can be viewed at http://wileyonlinelibrary.com]