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Endocr Rev. 2018 Aug 1;39(4):389-423. doi: 10.1210/er.2017-00212.

Klinefelter Syndrome: Integrating Genetics, Neuropsychology, and Endocrinology.

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Department of Endocrinology and Internal Medicine (MEA), Aarhus University Hospital, Aarhus C, Denmark.
Department of Molecular Medicine, Aarhus University Hospital, Aarhus N, Denmark.
Department of Clinical Biochemistry, Esbjerg Sygehus, Esbjerg, Denmark.
Department of Linguistics, Cognitive Science, and Semiotics, Aarhus University, Aarhus C, Denmark.
Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus C, Denmark.
Centre of Andrology and Fertility Clinic, Department of Gynaecology and Obstetrics, Odense University Hospital, Odense C, Denmark.
Department of Psychology, The George Washington University, Washington DC.
Department of Clinical Genetics, Aarhus University Hospital, Aarhus N, Denmark.


Although first identified over 70 years ago, Klinefelter syndrome (KS) continues to pose substantial diagnostic challenges, as many patients are still misdiagnosed, or remain undiagnosed. In fact, as few as 25% of patients with KS are accurately diagnosed and most of these diagnoses are not made until adulthood. Classic characteristics of KS include small testes, infertility, hypergonadothropic hypogonadism, and cognitive impairment. However, the pathophysiology behind KS is not well understood, although genetic effects are also thought to play a role. For example, recent developments in genetics and genomics point to a fundamental change in our understanding of KS, with global epigenetic and RNA expression changes playing a central role for the phenotype. KS is also associated with more general health markers, including higher morbidity and mortality rates and lower socioeconomic status (which likely affect both morbidity and mortality). In addition, hypogonadism is associated with greater risk of metabolic syndrome, type 2 diabetes, cardiovascular disease, breast cancer, and extragonadal germ cell tumors. Medical treatment typically focuses on testosterone replacement therapy (TRT), although the effects of this therapy have not been studied rigorously, and future studies need to evaluate the effects of TRT on metabolic risk and neurocognitive outcomes. This review presents a comprehensive interdisciplinary examination of recent developments in genetic, endocrine, and neurocognitive science, including the study of animal models. It provides a number of recommendations for improving the effectiveness of research and clinical practice, including neonatal KS screening programs, and a multidisciplinary approach to KS treatment from childhood until senescence.

[Indexed for MEDLINE]

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