![]() SIGNIFICANCE STATEMENT Sex and sex-chromosome dosage (SCD) are known to modulate human brain size and cortical anatomy, but very little is known regarding their impact on subcortical structures that work with the cortex to subserve a range of behaviors in health and disease. Our study provides a novel understanding of sex and sex-chromosome dosage effects on subcortical organization, using an allometric approach that can be generalized to other basic and clinical structural neuroimaging settings. Allometric analysis of SCA reveals that supernumerary X- and Y- chromosomes both cause disproportionate reductions in PV, and coordinated deformations of striatopallidal shape. Allometric analysis restricts sex-differences to: (1) greater pallidal volume (PV) in males, and (2) relative caudate head expansion and ventral striatum contraction in females. Traditional TBV correction methods assume linear scaling and can therefore invert or exaggerate sex and SCA effects on subcortical anatomy. We show that all three subcortical volumes scale sublinearly with TBV among healthy humans, mirroring known relationships between subcortical volume and TBV among species. We correct for TBV effects with a novel allometric method harnessing normative scaling rules for subcortical size and shape in humans, which we derive here for the first time. We find large effect-size differences in the volume and shape of all three structures as a function of sex and SCA. Here, in a cohort of 354 humans with varying karyotypes (XX, XY, XXX, XXY, XYY, XXYY, XXXXY), we investigate sex and SCA effects on subcortical size and shape focusing on the striatum, pallidum and thalamus. Structural neuroimaging of humans with typical and atypical sex-chromosome complements has established the marked influence of both Yand X-/Y- chromosome dosage on total brain volume (TBV) and identified potential cortical substrates for the psychiatric phenotypes associated with sex-chromosome aneuploidy (SCA). The effects on physical and cognitive development increase with the number of extra Xs, and each extra X is associated with an intelligence quotient (IQ decrease of approximately 15–16 points, with language most affectedĪn Allometric Analysis of Sex and Sex Chromosome Dosage Effects on Subcortical Anatomy in HumansĬlasen, Liv Giedd, Jay N. Androgen replacement therapy should begin at puberty, around age 12 years, in increasing dosage sufficient to maintain age appropriate serum concentrations of testosterone, estradiol, follicle stimulating hormone (FSH, and luteinizing hormone (LH. Adults are often evaluated for infertility or breast malignancy. The older child or adolescent may be discovered during an endocrine evaluation for delayed or incomplete pubertal development with eunuchoid body habitus, gynecomastia, and small testes. The school-aged child may present with language delay, learning disabilities, or behavioral problems. ![]() In infancy, males with 47,XXY may have chromosomal evaluations done for hypospadias, small phallus or cryptorchidism, developmental delay. If the diagnosis is not made prenatally, 47,XXY males may present with a variety of subtle clinical signs that are age-related. Formal cytogenetic analysis is necessary to make a definite diagnosis, and more obvious differences in physical features tend to be associated with increasing numbers of sex chromosomes. In addition, 46,XX males also exist and it is caused by translocation of Y material including sex determining region (SRY to the X chromosome during paternal meiosis. The incidence of 49, XXXXY is 1 per 85,000 to 100,000 male births. Other sex chromosomal aneuploidies have also been described, although they are much less frequent, with 48,XXYY and 48,XXXY being present in 1 per 17,000 to 1 per 50,000 male births. ![]() XXY aneuploidy is the most common disorder of sex chromosomes in humans, with prevalence of one in 500 males. Klinefelter syndrome and other sex chromosomal aneuploidiesĭirectory of Open Access Journals (Sweden)įull Text Available Abstract The term Klinefelter syndrome (KS describes a group of chromosomal disorder in which there is at least one extra X chromosome to a normal male karyotype, 46,XY. Klinefelter Syndrome Trisomy X XYY Syndrome XXXY and XXXXY Syndrome Xxyy Syndrome Xyyy Syndrome Xxxx Syndrome Xxxxx Syndrome Xxxyy Syndrome Xxyyy Syndrome Xyyyy Syndrome Male With Sex Chromosome Mosaicism The eXtroardinarY Babies Study: Natural History of Health and Neurodevelopment in Infants and Young Children With Sex Chromosome Trisomy
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