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      Early Androgen Deficiency in Infants and Young Boys with 47,XXY Klinefelter Syndrome

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          Background/Aims: Klinefelter syndrome (KS) is characterized by the karyotype 47,XXY. In this study, we evaluated the physical and testicular failure phenotypes of infants and young boys with KS. Methods: The evaluation included auxologic measurements, biologic indices of testicular function, and clinical assessment of muscle tone in 22 infants and young boys with KS, ages 1–23 months. Results: Mean length, weight, and head circumference in SDS were generally within the normal range at –0.3 ± 1.0, –0.1 ± 1.4, and 0.0 ± 1.5, respectively. Mean penile length and testicular volume SDS were –0.9 ± 0.8 and –1.1 ± 0.8, indicating significantly reduced penile and testicular size. Mean testosterone levels for the boys ≤6 and >6–23 months were 128 ± 131 (4.4 ± 4.5 nmol/l) and 9.5 ± 7.2 ng/dl (0.3 ± 0.2 nmol/l), respectively. High-arched palate was observed in 6/17 boys and clinodactyly (5th finger) was observed in 15/16 boys. Hypotonia was evaluated clinically and was noted to be present in 12/17 boys. Conclusion: The physical phenotype in infants and young boys with KS (1–23 months old) includes normal auxologic measurements and early evidence of testicular failure. Muscle tone was decreased in most of the boys. Testicular volume and penile length were diminished, indicating early androgen deficiency. The neonatal surge in testosterone was attenuated in our KS population. Thus, infants and young boys with KS have evidence of early testicular failure. The etiology of this failure and the clinical role of early androgen replacement require further study.

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          Most cited references 19

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          An abundance of X-linked genes expressed in spermatogonia.

          Spermatogonia are the self-renewing, mitotic germ cells of the testis from which sperm arise by means of the differentiation pathway known as spermatogenesis. By contrast with hematopoietic and other mammalian stem-cell populations, which have been subjects of intense molecular genetic investigation, spermatogonia have remained largely unexplored at the molecular level. Here we describe a systematic search for genes expressed in mouse spermatogonia, but not in somatic tissues. We identified 25 genes (19 of which are novel) that are expressed in only male germ cells. Of the 25 genes, 3 are Y-linked and 10 are X-linked. If these genes had been distributed randomly in the genome, one would have expected zero to two of the genes to be X-linked. Our findings indicate that the X chromosome has a predominant role in pre-meiotic stages of mammalian spermatogenesis. We hypothesize that the X chromosome acquired this prominent role in male germ-cell development as it evolved from an ordinary, unspecialized autosome.
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            Prenatal and postnatal prevalence of Klinefelter syndrome: a national registry study.

            The objective of this study was to describe the prevalence of Klinefelter syndrome (KS) prenatally and postnatally in Denmark and determine the influence of maternal age. All chromosomal examinations in Denmark are registered in the Danish Cytogenetic Central Registry. Individuals with KS diagnosed prenatally or postnatally were extracted from the registry with information about age at the time of diagnosis and mother's age. In the period 1970-2000, 76,526 prenatal examinations on male fetuses resulted in the diagnosis of 163 fetuses with KS karyotype, corresponding to a prevalence of 213 per 100,000 male fetuses. Standardization according to maternal age resulted in a prevalence of 153 per 100,000 males. Postnatally, 696 males of 2,480,858 live born were diagnosed with KS, corresponding to a prevalence among adult men of approximately 40 per 100,000. Less than 10% of the expected number was diagnosed before puberty. Advanced maternal age had a significant impact on the prevalence. KS is severely underdiagnosed in Denmark. Only approximately one fourth of adult males with KS are diagnosed. There is a marked delay in diagnosis of the syndrome. A delay in treatment with testosterone may lead to decreased muscle and bone mass with subsequent risk of osteoporosis.
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              Hypophyso-gonadal function in humans during the first year of life. 1. Evidence for testicular activity in early infancy.

              Total and unbound testosterone and Delta(4)-androstenedione have been determined in 104 cord blood samples. The same sexual steroids and pituitary gonadotropins have been measured in 46 normal male infants aged 27-348 days and 34 normal female infants aged 19-332 days. In cord blood of female neonates mean total and unbound testosterone was 29.6+/-7.5 and 0.89+/-0.4 ng/100 ml, respectively (mean+/-1 SD); Delta(4)-androstenedione was 93+/-38 ng/100 ml. In male neonates mean plasma total and unbound testosterone was 38.9+/-10.8 and 1.12+/-0.4 ng/100 ml; Delta(4)-androstenedione was 85+/-27 ng/100 ml. In female infants testosterone concentrations remained constant during the 1st yr of life with a mean concentration of 7+/-3 ng/100 ml. Mean unbound testosterone and Delta(4)-androstenedione concentrations were 0.05+/-0.03 and 16.7+/-8.3 ng/100 ml, respectively. Mean plasma levels of follicle-stimulating hormone and luteinizing hormone were 8.7+/-3.3 and 12.9+/-7.7 mU/ml. In male infants mean plasma total testosterone concentration increased to 208+/-68 ng/100 ml from birth to 1-3 mo of age, decreasing thereafter to 95+/-53 ng/100 ml at 3-5 mo, 23.2+/-18 ng/100 ml at 5-7 mo, and reached prepubertal levels (6.6+/-4.6 ng/100 ml) at 7-12 mo. Mean unbound testosterone concentration plateaued from birth to 1-3 mo of age (1.3+/-0.2 ng/100 ml) decreasing to prepubertal values very rapidly. Mean Delta(4)-androstenedione concentration, although progressively decreasing during the 1st yr of life to 11.7+/-4.5 ng/100 ml, was higher than in the female at 1-3 mo of life (34+/-11 ng/100 ml). Mean plasma level of follicle-stimulating hormone was 6.7+/-2.9 mU/ml, and that of luteinizing hormone was 19.7+/-13.5 mU/ml, significantly higher than in the female. There was no correlation between gonadotropin and age or testosterone. The present data demonstrate that the testes are active during the first natal period. It is tempting to correlate this phenomenon to a progressive maturation of the hypothalamo-pituitary-gonadal axis. It is possible that the surge in testosterone occurring the first 3 mo could play a role in the future life pattern of the male human being.

                Author and article information

                Horm Res Paediatr
                Hormone Research in Paediatrics
                S. Karger AG
                September 2005
                31 August 2005
                : 64
                : 1
                : 39-45
                aDepartment of Pediatrics, Thomas Jefferson University, Philadelphia, Pa.; bduPont Hospital for Children, Wilmington, Del.; cEugene McDermott Center for Human Growth and Development, and Department of Internal Medicine, The University of Texas Southwestern Medical School, Dallas, Tex.; dDepartment of Pathology, The University of Texas Southwestern Medical School, Dallas, Tex.; eThe Neurodevelopment Diagnostic Center, Department of Pediatrics, The George Washington University, Washington, D.C., USA; fLaboratoire de Biologie Hormonale, Hôpital Saint-Vincent-de-Paul, Paris, France
                87313 Horm Res 2005;64:39–45
                © 2005 S. Karger AG, Basel

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                Page count
                Figures: 3, Tables: 2, References: 52, Pages: 7
                Original Paper


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