Morbidity and mortality in Klinefelter syndrome (47,XXY)

Gender identity in Klinefelter Syndrome: a patient-centered approach to treatment

INTRODUCTION

There is increasing evidence that gender dysphoria (GD) is more prevalent in the Klinefelter Syndrome (KS) population than in males in the general population; however, the exact incidence is uncertain. The aim of this study was to further explore the prevalence of gender-related issues, the role that physical characteristics play in gender identity, and the issues surrounding Hormone Replacement Therapy (HRT) in KS.

METHODS

As part of a registered Quality Improvement Project (QIP), one online 23-point questionnaire on KS patient attitudes toward gender identity was shared with members of the Klinefelter Syndrome Association (KSA). In total, 139 anonymous responses were collected between December 2021 and January 2023. The questionnaire was developed with the guidance of multiple clinicians (including gender psychiatrists, urologists, psychosexual medicine specialists, and endocrinologists) and patient Delphi rounds. Data was reviewed and analyzed by 4 independent researchers within the QIP team.

RESULTS

Only 53% of KS patients responding to this survey fully identified as male and 19% stated that they did not enjoy living as the sex on their birth certificate, with 43% considering changing aspects of their physical appearance to better match their gender. Regarding HRT, 67% of respondents were receiving Testosterone Replacement Therapy (TRT). 63% wanted TRT and 17% wanted estrogen, including 6% of TRT users who would prefer estrogen instead. 36% that were currently receiving TRT did not identify as male, and 3 participants stated that they have GD.

CONCLUSION

These results indicate that a significant proportion of KS patients do not fully identify with the male gender and are unhappy living as the sex on their birth certificate. Although TRT worked for most, its use should be discussed carefully with those with gender identity concerns.

Inhibitory deficits in Klinefelter syndrome are secondary to deficits in the auditory and motor domain

Deficits in several cognitive domains are prevalent in men with Klinefelter Syndrome (KS). Verbal deficits are among the most characteristic cognitive impairments of KS, yet other cognitive domains also exhibit deficits. Executive functions, especially working memory capacity and inhibitory control, are frequently affected as well. A common limitation of previous studies addressing potential deficits in inhibitory control is their potential conflation with language-related capabilities, as for example is the case with the Stroop task. Importantly, none of the prior studies utilized the best-accepted approach to study inhibition, namely the Stop Signal Task (SST). This study therefore tested for deficits in inhibitory control in individuals with KS and controls (HC) using a version of the SST with non-semantic auditory stimuli. In addition to the classic behavioral performance measures (e.g., the go reaction time, stopping accuracy, or stop signal reaction time), we also derived parameters of inhibition and attention from electromyography (EMG), electroencephalography (EEG), and Bayesian modeling. Men with KS exhibited prolonged stopping latencies (i.e., stop signal reaction times) and reduced stopping accuracies. Yet, whereas these model-based indices were indicative of attenuated inhibitory control, neither event-related brain potentials nor an EMG-measure of the stopping latency confirmed such deficits. Behavioral and EEG indices, however, provided evidence for deficits in motor response preparation and generation, as well as the early processing of auditory stimuli. In sum, the overall pattern of results does not support the existence of inhibitory deficits in KS per se, but rather suggests that behavioral indices of impaired inhibition may result from early low-level deficits in the auditory and motor domains, as well as a differential weighting in the processing of different aspects of the task.

X‑chromosome loss rescues Sertoli cell maturation and spermatogenesis in Klinefelter syndrome

Klinefelter syndrome (47,XXY) causes infertility with a testicular histology comprising two types of Sertoli cell-only tubules, representing mature and immature-like Sertoli cells, and occasionally focal spermatogenesis. Here, we show that the immature-like Sertoli cells highly expressed XIST and had two X-chromosomes, while the mature Sertoli cells lacked XIST expression and had only one X-chromosome. Sertoli cells supporting focal spermatogenesis also lacked XIST expression and the additional X-chromosome, while the spermatogonia expressed XIST despite having only one X-chromosome. XIST was expressed in Sertoli cells until puberty, where a gradual loss was observed. Our results suggest that a micro-mosaic loss of the additional X-chromosome is needed for Sertoli cells to mature and to allow focal spermatogenesis.

Prevalence, Morbidity, and Mortality of 1,609 Men with Sex Chromosome Aneuploidy: Results from the Diverse Million Veteran Program Cohort

Importance

The reported phenotypes of men with 47,XXY and 47,XYY syndromes include tall stature, multisystem comorbidities, and poor health-related quality of life (HRQoL). However, knowledge about these sex chromosome aneuploidy (SCA) conditions has been derived from studies in the <15% of patients who are clinically diagnosed and also lack diversity in age and genetic ancestry.

Objectives

Determine the prevalence of clinically diagnosed and undiagnosed X or Y chromosome aneuploidy among men enrolled in the Million Veteran Program (MVP); describe military service metrics of men with SCAs; compare morbidity and mortality outcomes between men with SCA with and without a clinical diagnosis to matched controls.

Design

Cross-sectional, case-control.

Setting

United States Veterans Administration Healthcare System.

Participants

Biologic males enrolled in the MVP biobank with genomic identification of an additional X or Y chromosome (cases); controls matched 1:5 on sex, age, and genetic ancestry.

Main Outcomes and Measures

Prevalence of men with SCAs from genomic analysis; clinical SCA diagnosis; Charlson Comorbidity Index (CCI); rates of outpatient, inpatient, and emergency encounters per year; self-reported health outcomes; standardized mortality ratio (SMR).

Results

An additional X or Y chromosome was present in 145 and 125 per 100,000 males in the MVP, respectively, with the highest prevalence among men with European and East Asian ancestry. At a mean age of 61±12 years, 74% of male veterans with 47,XXY and >99% with 47,XYY remained undiagnosed. Individuals with 47,XXY (n=862) and 47,XYY (n=747) had similar military service history, all-cause SMR, and age of death compared to matched controls. CCI and healthcare utilization were higher among individuals with SCA, while several measures of HRQoL were lower. Men with a clinical diagnosis of 47,XXY had higher healthcare utilization but lower comorbidity score compared to those undiagnosed.

Conclusion and Relevance

One in 370 males in the MVP cohort have SCA, a prevalence comparable to estimates in the general population. While these men have successfully served in the military, they have higher morbidity and report poorer HRQoL with aging. Longer longitudinal follow-up of this sample will be informative for clinical and patient-reported outcomes, the role of ancestry, and mortality statistics.

KEY POINTS

Comparable to the general population, approximately 1 in 370 male veterans have a sex chromosome aneuploidy, but most are undiagnosed.Men with X or Y chromosome aneuploidy successfully complete US miliary duty with similar service history compared to their 46,XY peers.Medical comorbidities and healthcare utilization metrics are higher in male veterans with 47,XXY and 47,XYY during aging, however life expectancy is similar to matched controls.

X chromosome dosage and the genetic impact across human tissues

BACKGROUND

Sex chromosome aneuploidies (SCAs) give rise to a broad range of phenotypic traits and diseases. Previous studies based on peripheral blood samples have suggested the presence of ripple effects, caused by altered X chromosome number, affecting the methylome and transcriptome. Whether these alterations can be connected to disease-specific tissues, and thereby having clinical implication for the phenotype, remains to be elucidated.

METHODS

We performed a comprehensive analysis of X chromosome number on the transcriptome and methylome in blood, fat, and muscle tissue from individuals with 45,X, 46,XX, 46,XY, and 47,XXY.

RESULTS

X chromosome number affected the transcriptome and methylome globally across all chromosomes in a tissue-specific manner. Furthermore, 45,X and 47,XXY demonstrated a divergent pattern of gene expression and methylation, with overall gene downregulation and hypomethylation in 45,X and gene upregulation and hypermethylation in 47,XXY. In fat and muscle, a pronounced effect of sex was observed. We identified X chromosomal genes with an expression pattern different from what would be expected based on the number of X and Y chromosomes. Our data also indicate a regulatory function of Y chromosomal genes on X chromosomal genes. Fourteen X chromosomal genes were downregulated in 45,X and upregulated in 47,XXY, respectively, in all three tissues (AKAP17A, CD99, DHRSX, EIF2S3, GTPBP6, JPX, KDM6A, PP2R3B, PUDP, SLC25A6, TSIX, XIST, ZBED1, ZFX). These genes may be central in the epigenetic and genomic regulation of sex chromosome aneuploidies.

CONCLUSION

We highlight a tissue-specific and complex effect of X chromosome number on the transcriptome and methylome, elucidating both shared and non-shared gene-regulatory mechanism between SCAs.

Oncological diseases in Klinefelter Syndrome: an overview

Epidemiological studies have highlighted a higher incidence of morbidity and mortality among individuals with Klinefelter's Syndrome (KS), however, the relative impact of oncological diseases on KS subjects is still uncertain. While some malignancies (e.g., hematological and lung cancers) may show an increased prevalence in the KS population, only a few rare tumors (i.e., extragonadal germ cell tumors [GCTs] and male breast cancer [MBC]) seem to follow this trend. Additionally, hormonal and genetic determinants may be involved in the pathogenesis of neoplasia in KS, even if subjects affected by this syndrome generally show lower incidence of prostate cancer along with lower disease-specific mortality despite testosterone replacement therapy (TRT). This review deals with the pathophysiological and clinical aspects of neoplastic diseases occurring in KS.

Testosterone deficiency and metabolic disturbances in men who fathered a child by use of donated spermatozoa

Dose–response association between level of impairment of semen quality and risk of morbidity or premature death has been reported. Therefore, it can be presumed that men utilizing donated spermatozoa, i.e. patients with non-obstructive azoospermia, are at highest risk for adverse health outcomes. To evaluate the risks of prescription of medications for common metabolic disturbances and testosterone replacement therapy (TRT) among men who father children with donated spermatozoa—who presumably do it due to severe impairment of fertility. We used Swedish nationwide register data on all fathers who had a live-born child between 2007 and 2014 in order to compare men who fathered children with donated spermatozoa to the ones who became fathers by using own gametes. Cox regression analysis was used in order to estimate the post-conception incidence of prescription of medicines for hypertension (HT), diabetes (type 1 and 2), dyslipidaemia (DLE) or TRT. Starting the follow up at time of conception, models were adjusted for age, educational level, and previous cancer treatment. In total 410,119 childbirths were included in the analysis. Among them, for 390 fathers donated spermatozoa were utilized. Fathers to children conceived with donated spermatozoa had higher risk for having TRT prescribed (HR: 18.14; 95%CI: 11.71–28.10; p ≪ 0.001). Same was true for DLE (HR: 2.08; 95%CI: 1.27–3.39; p = 0.003) but not diabetes. Fathers to children conceived by use of donated spermatozoa are at significantly increased risk for testosterone treatment and dyslipidaemia, necessitating stringent follow up and inclusion in prevention programs.

Metabolic and Nutritional Aspects in Paediatric Patients with Klinefelter Syndrome: A Narrative Review

Klinefelter syndrome is the most common sex chromosomal aneuploidy in males. It is well known that patients with this syndrome have greater mortality and morbidity compared to the general population due to cardiovascular diseases and endocrine metabolism disorders. This augmented risk is due both to hypogonadism and to the syndrome itself. Therefore, correct hormonal replacement therapy and early primary prevention are crucial to these patients. Even though different studies are available on this topic in adult patients, only a few authors have focused on the paediatric population. Thus, in this narrative review, we report the current knowledge of metabolic and nutritional aspects in children with Klinefelter syndrome.

Population-based Assessment of Cardiometabolic-related Diagnoses in Youth With Klinefelter Syndrome: A PEDSnet Study

CONTEXT

Diabetes and cardiovascular diseases are common among men with Klinefelter syndrome (KS) and contribute to high morbidity and mortality.

OBJECTIVE

To determine if cardiometabolic-related diagnoses are more prevalent among youth with KS than matched controls in a large population-based cohort.

METHODS

Secondary data analysis of electronic health records from 6 pediatric institutions in the United States (PEDSnet). Patients included all youth with KS in the database (n = 1080) and 4497 youth without KS matched for sex, age (mean 13 years at last encounter), year of birth, race, ethnicity, insurance, site, and duration of care (mean 7 years). The main outcome measures were prevalence of 5 cardiometabolic-related outcomes: overweight/obesity, dyslipidemia, dysglycemia, hypertension, and liver dysfunction.

RESULTS

The odds of overweight/obesity (OR 1.6; 95% CI 1.4-1.8), dyslipidemia (3.0; 2.2-3.9), and liver dysfunction (2.0; 1.6-2.5) were all higher in KS than in controls. Adjusting for covariates (obesity, testosterone treatment, and antipsychotic use) attenuated the effect of KS on these outcomes; however, boys with KS still had 45% greater odds of overweight/obesity (95% CI 1.2-1.7) and 70% greater odds of liver dysfunction (95% CI 1.3-2.2) than controls, and both dyslipidemia (1.6; 1.1-2.4) and dysglycemia (1.8; 1.1-3.2) were higher in KS but of borderline statistical significance when accounting for multiple comparisons. The odds of hypertension were not different between groups.

CONCLUSION

This large, population-based cohort of youth with KS had a higher odds of most cardiometabolic-related diagnoses than matched controls.

Cortical Bone Mass is Low in Boys with Klinefelter Syndrome and Improves with Oxandrolone

Context

Klinefelter syndrome (KS) is the most common sex aneuploidy in men. Affected males have hypogonadism, and, as a result, face an increased risk for osteoporosis and fractures. Androgen therapy is standard in adolescents and adults with KS but has not been used earlier in childhood.

Objective

To determine the effects of androgen treatment on bone mass in children with KS.

Methods

Randomized, double-blind, placebo-controlled clinical trial of oxandrolone (OX; 0.06 mg/kg daily; n = 38) versus placebo (PL; n = 40) for 2 years in boys with KS (ages 4-12 years). Changes in bone mass were examined by digital x-ray radiogrammetry, which determines the Bone Health Index (BHI) and standard deviation score (SDS).

Results

BHI SDS was similar between groups at baseline (–0.46 ± 1.1 vs –0.34 ± 1.0 OX vs PL, P > .05) and higher in the OX group at 2 years (–0.1 ± 1.3 vs –0.53 ± 0.9, OX vs PL, P < .01). At baseline, BHI SDS values of all subjects were not normally distributed with 25.7% of subjects plotted below –1 SDS (P < .001), suggesting a deficit in bone mass. In total, 13.5% of subjects had sustained a fracture and their BHI SDS was lower than those with no fractures (–1.6 ± 1.3 vs –0.3 ± 1.0, P = .004).

Conclusion

Bone mass using BHI SDS is reduced in some children with KS and improves with OX. Since these individuals are at risk for osteoporosis, age-appropriate androgen replacement and future studies on bone health in children with KS should be further explored.

[Klinefelter syndrome: literature review on using modern methods of assisted reproductive technologies]

The article reviews scientific papers devoted to the problem of reproductive health in men with Klinefelter syndrome (KS). Pathogenesis from a very early age (in utero), the possibility of ensuring biological paternity upon reaching sexual maturity and the risk of chromosomal abnormalities in offspring are discussed. Despite the fact that KS is one of the most common causes of male infertility associated with chromosomal abnormalities, due to the variability of clinical manifestations the proportion of patients identified before puberty did not exceed 10% before the widespread introduction of non-invasive prenatal testing. According to the research results presented in the article, the reproductive potential of males with KS is often already reduced in early childhood. These circumstances should be considered when choosing further patient management tactics.There are few reports on the onset of spontaneous pregnancy in the case of KS, so ensuring biological paternity in this group of patients is often possible only using surgical methods of sperm extraction and assisted reproductive technologies. This article discusses methods like testicular sperm extraction (TESE) and microdissection testicular sperm extraction (mTESE) in terms of their effectiveness and safety for the patient, and the factors influencing the outcome of the operation. The optimal period of these manipulations seems to be the patient's age from 18 to 30 years, although the feasibility of adolescent boys undergoing the aforementioned procedures is highly controversial.The research papers presented in the article suggest that the risk of transmitting chromosomal abnormalities to offspring is rather low, which does not exclude the need for medical and genetic counseling to explain all possible risks to the patient. Preimplantation or intrauterine diagnostics are also deemed necessary.

Cardiovascular Complications in Patients with Klinefelter's Syndrome

More than 70 years have passed since the first description of Klinefelter Syndrome (KS), the most frequent chromosome disorder causing male infertility and hypogonadism. KS is associated with increased cardiovascular (CV) mortality due to several comorbidities, including hypogonadism, as well as metabolic syndrome and type 2 diabetes, which are highly prevalent in these patients. Aside from metabolic disturbances, patients with KS suffer from both acquired and congenital CV abnormalities, cerebrovascular thromboembolic disease, subclinical atherosclerosis and endothelial dysfunction, which may all contribute to increased CV mortality. The mechanisms involved in this increased risk of CV morbidity and mortality are not entirely understood. More research is needed to better characterise the CV manifestations, elucidate the pathophysiological mechanisms and define the contribution of testosterone replacement to restoring CV health in KS patients. This review explores the complex association between KS, metabolic syndrome and CV risk in order to plan future studies and improve strategies to reduce mortality in this high-risk population.

Male factor infertility and risk of death: a nationwide record-linkage study

STUDY QUESTION

What is the risk of death among men with oligospermia, unspecified male factor and azoospermia in the years following fertility treatment?

SUMMARY ANSWER

No significantly elevated risk was observed among men with oligospermia and unspecified male factor, while an increased risk was found among men with azoospermia.

WHAT IS KNOWN ALREADY

Previous studies have shown associations between male factor infertility and risk of death, but these studies have relied on internal reference groups and the risk of death according to type of male infertility is not well characterized.

STUDY DESIGN, SIZE, DURATION

In this prospective record-linkage cohort study, we identified men who had undergone medically assisted reproduction (MAR) between 1994 and 2015. Data was linked to the Danish causes of death register and sociodemographic registers through personal identification numbers assigned to all Danish citizens at birth.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Men that had undergone MAR in Denmark (MAR Cohort; n = 64 563) were identified from the Danish IVF register, which includes data on whether infertility was due to male factor. For each man in the MAR cohort, five age-matched men who became fathers without fertility treatment were selected from the general population (non-MAR fathers; n = 322 108). Men that could not adequately be tracked in the Danish CPR register (n = 1259) and those that were censored prior to study entry (n = 993) were excluded, leaving a final population of 384 419 men. Risk of death was calculated by Cox regression analysis with age as an underlying timeline and adjustments for educational attainment, civil status and year of study entry. The risk of death was compared among men with and without male factor infertility identified from the IVF register (internal comparisons) as well as to the non-MAR fathers (external comparison).

MAIN RESULTS AND THE ROLE OF CHANCE

The risk of death between the MAR cohort (all men, regardless of infertility) and the non-MAR fathers was comparable [hazard ratio (HR), 1.07; 95% CI, 0.98-1.15]. When the MAR cohort was limited to infertile men, these men were at increased risk of death [HR, 1.27; 95% CI, 1.12-1.44]. However, when stratified by type of male factor infertility, men with azoospermia had the highest risk of death, which persisted when in both the internal [HR, 2.30; 95% CI, 1.54-3.41] and external comparison [HR, 3.32; 95% CI, 2.02-5.40]. No significantly elevated risk of death was observed among men with oligospermia [HR, 1.14; 95% CI, 0.87-1.50] and unspecified male factor [HR, 1.10; 95% CI, 0.75-1.61] compared with the non-MAR fathers. The same trends were observed for the internal comparison.

LIMITATIONS, REASONS FOR CAUTION

Duration of the follow-up was limited and there is limited generalizability to infertile men who do not seek fertility treatment.

WIDER IMPLICATIONS OF THE FINDINGS

Using national health registers, we found an increased risk of death among azoospermic men while no increased risk was found among men with other types of infertility. For the azoospermic men, further insight into causal pathways is needed to identify options for monitoring and prevention.

STUDY FUNDING/COMPETING INTEREST(S)

This study is part of the ReproUnion collaborative study, co-financed by the European Union, Interreg V ÖKS. C.G.'s research stay at Stanford was funded by grants from the University of Copenhagen, Kong Christian den Tiendes Fond, Torben og Alice Frimodt Fond and Julie Von Müllen Fond. M.E. is an advisor for Sandstone and Dadi. All other authors declare no conflict of interests.

TRIAL REGISTRATION NUMBER

Not relevant.

Chromosomal abnormalities and atrial fibrillation and ischemic stroke incidence: a nationwide population-based study

There is a paucity of information as to whether chromosomal abnormalities, including Down Syndrome, Turner Syndrome, and Klinefelter Syndrome, have an association with atrial fibrillation (AF) and ischemic stroke development. Data from 3660 patients with Down Syndrome, 2408 with Turner Syndrome, and 851 with Klinefelter Syndrome without a history of AF and ischemic stroke were collected from the Korean National Health Insurance Service (2007–2014). These patients were followed-up for new-onset AF and ischemic stroke. Age- and sex-matched control subjects (at a ratio of 1:10) were selected and compared with the patients with chromosomal abnormalities. Down Syndrome patients showed a higher incidence of AF and ischemic stroke than controls. Turner Syndrome and Klinefelter Syndrome patients showed a higher incidence of AF than did the control group, but not of stroke. Multivariate Cox regression analysis revealed that three chromosomal abnormalities were independent risk factors for AF, and Down Syndrome was independently associated with the risk of stroke. In conclusion, Down Syndrome, Turner Syndrome, and Klinefelter Syndrome showed an increased risk of AF. Down Syndrome patients only showed an increased risk of stroke. Therefore, AF surveillance and active stroke prevention would be beneficial in patients with these chromosomal abnormalities.

High prevalence of cardiometabolic risk features in adolescents with 47,XXY/Klinefelter syndrome

Klinefelter syndrome (KS) occurs in 1:600 males and is associated with high morbidity and mortality due to diabetes and cardiovascular disease. Up to 50% of men with KS have metabolic syndrome, a cluster of features conferring increased risk for diabetes and cardiovascular disease. These cardiometabolic (CM) risk features have not been studied in adolescents with KS. The objective of this cohort study was to compare CM risk features in adolescents with KS to controls matched for sex, age, and BMI z score. Fifty males with KS (age 10-17 years) were well-matched to male controls (n = 50) for age (14.0 ± 1.7 vs. 14.0 ± 1.5 years) and BMI z score (0.3 ± 1.3 vs. 0.4 ± 1.2). Three CM risk features were present in 30% of adolescents with KS compared to 12% of controls (RR 2.5, 95% CI 1.1-5.9, p = .048). The KS group had significantly lower HDL cholesterol (p = .006), higher triglycerides (p < .001), and greater waist circumference percentile (p < .001). Despite a normal BMI, the prevalence of CM risk features was very high in adolescents with KS, particularly for central adiposity and dyslipidemia. The pathophysiology of this metabolic profile independent of obesity needs further investigation to facilitate prevention of the high morbidity of cardiovascular disease and diabetes in this population. ClinicalTrials.gov identifiers: NCT01585831 and NCT02723305.

Early neurodevelopmental and medical profile in children with sex chromosome trisomies: Background for the prospective eXtraordinarY babies study to identify early risk factors and targets for intervention

Sex chromosome trisomies (SCT), including Klinefelter syndrome/XXY, Trisomy X, and XYY syndrome, occur in 1 of every 500 births. The past decades of research have resulted in a broadening of known associated medical comorbidities as well as advances in psychological research. This review summarizes what is known about early neurodevelopmental, behavioral, and medical manifestations in young children with SCT. We focus on recent research and unanswered questions related to the risk for neurodevelopmental disorders that commonly present in the first years of life and discuss the medical and endocrine manifestations of SCT at this young age. The increasing rate of prenatal SCT diagnoses provides the opportunity to address gaps in the existing literature in a new birth cohort, leading to development of the eXtraordinarY Babies Study. This study aims to better describe and compare the natural history of SCT conditions, identify predictors of positive and negative outcomes in SCT, evaluate developmental and autism screening measures commonly used in primary care practices for the SCT population, and build a rich data set linked to a bank of biological samples for future study. Results from this study and ongoing international research efforts will inform evidence-based care and improve health and neurodevelopmental outcomes.

41,XXY * male mice: An animal model for Klinefelter syndrome

Klinefelter syndrome (KS, 47,XXY) is the most frequent male chromosomal aneuploidy resulting in a highly heterogeneous clinical phenotype associated with hormonal dysbalance, increased rate of co-morbidities, and reduced lifespan. Two hallmarks of KS-affecting testicular functions are consistently observed: Hypergonadotropic hypogonadism and germ cell (GC) loss resulting in infertility. Although KS is being studied for decades, the underlying mechanisms for the observed pathophysiology are still unclear. Due to ethical restrictions, studies in humans are limited, and consequently, suitable animal models are needed to address the consequences of a supernumerary X chromosome. Mouse strains with comparable aneuploidies have been generated and yielded highly relevant insights into KS. We briefly describe the establishment of the KS mouse models, summarize the knowledge gained by their use, compare findings from the mouse models to those obtained in clinical studies, and also reflect on limitations of the currently used models derived from the B6Ei.Lt-Y* mouse strain, in which the Y chromosome is altered and its centromere position changed into a more distal location provoking meiotic non-disjunction. Breeding such as XY* males to XX females, the target 41,XX^Y *, and 41,XXY males are generated. Here, we summarize features of both models but report in particular findings from our 41,XX^Y * mice including some novel data on Sertoli cell characteristics.

Germ cell loss in Klinefelter syndrome: When and why?

Klinefelter syndrome (KS) is a quite common disorder with an incidence of 1-2 in 1,000 new-born males. Most patients are diagnosed in the light of a clinical checkup when consulting a fertility clinic with an unfulfilled child wish. Infertility in KS patients is caused by a massive germ cell loss, leading to azoospermia in more than 90% of the adult patients. Most seminiferous tubules in the adult KS testis are degenerated or hyalinized and testicular fibrosis can be observed, starting from puberty. However, focal spermatogenesis can be found in the testis of some patients. This offers the opportunity to extract spermatozoa from the testis by testicular sperm extraction (TESE). Nevertheless, TESE is only successful in about half of the KS adults seeking to father children. The reason for the germ cell loss remains unclear. To date, it is still debated whether the testicular tissue changes and the germ cell loss seen in KS is directly caused by an altered X-linked gene expression, the altered somatic environment, or a deficiency in the germ cells. In this review, we provide an overview of the current knowledge about the germ cell loss in KS patients.

Molecular Aging Markers in Patients with Klinefelter Syndrome

Molecular aging markers provide the opportunity for biological age determination in humans and to study factors, such as genetic determinants, affecting the ageing process. In males with Klinefelter syndrome (KS, non-mosaic karyotype 47, XXY), which is the most common sex chromosome aneuploidy, age-related morbidity and mortality are increased, and a significantly reduced life span has been observed. The aim of this study was to investigate whether Klinefelter patients exhibit molecular signs of premature ageing. We studied, specifically, age-associated DNA methylation patterns (by pyrosequencing) and relative telomere length (TL; by quantitative polymerase chain reaction) in blood in a cohort of Klinefelter patients (n=178 and 266 for DNA methylation and TL, respectively) aged 18-71 years and compared them to the data of age-matched healthy male (n = 184 and 196 for DNA methylation and TL, respectively) and female controls (n = 50). Age-associated DNA methylation patterns were not indicative of accelerated ageing in Klinefelter men. Significantly longer telomeres were found in the young Klinefelter subjects aged 18-24 years (mean=1.51 vs. 1.09 and 1.26 in female and male controls, respectively). However, telomere length in subsequent age groups showed no difference to controls. Gonosomal aneuploidy in Klinefelter syndrome is associated with higher baseline TL at adolescent age, but comparable TL with progressive age in other age groups.

Family experiences and attitudes about receiving the diagnosis of sex chromosome aneuploidy in a child

The most common sex chromosome aneuploidies (SCA) (47, XXY; 47, XYY; 47, XXX) frequently result in a milder phenotype than autosomal aneuploidies. Nevertheless, these conditions are highly variable and more symptomatic phenotypes may require significant clinical involvement, including specialty care. While historically most individuals with mild phenotypes remained undiagnosed during their lifetime, the increasing use of genetic testing in clinical care has increased the prenatal and postnatal diagnosis of SCAs. These genetic tests are frequently ordered by nongenetic providers who are also responsible for delivering the diagnosis. We surveyed parents of children (n = 308) to evaluate their experience of receiving a diagnosis and their support needs. The majority (73.3%) received the diagnosis from a nongenetic medical provider. Following a prenatal diagnosis parents reported experiencing depression, anxiety, and less optimism than those receiving a postnatal diagnosis. Few parents reported receiving materials explaining their child's condition that they found to be up-to-date, accurate, and unbiased. The frequently negative reported experiences of parents at time of diagnosis suggests more educational opportunities should be provided for nongenetic providers in order to become more informed about these conditions and communicate the diagnosis in a way parents experience as supportive.

Klinefelter syndrome and testosterone treatment: a national cohort study on thrombosis risk

OBJECTIVES

Klinefelter syndrome (KS), 47,XXY, can be viewed as a disease model for investigating the risk of thrombosis in male hypogonadism and the subsequent risk related to testosterone treatment. We describe rates of thrombotic risk factors, thrombosis and thrombosis mortality in KS and the association with testosterone treatment.

METHODS

National registry-based matched cohort study with follow-up from 1995 to 2016 set in Denmark. For the study, 1155 men with KS were each matched by year and month of birth to 100 men from the background population. First thrombotic events and thrombosis mortality was evaluated by event rates and hazard ratios (HRs) and by applying testosterone treatment as a time-dependent covariate.

RESULTS

The KS cohort had higher incidence of venous thromboembolism relative to the comparison cohort (HR, 3.95; 95% CI, 2.83-5.52). Total thrombotic deaths were increased in KS (HR, 1.76; 95% CI, 1.18-2.62), and all-cause mortality was increased in KS following arterial thrombosis (HR 1.73; 95% CI 1.22-2.47). Only 48.7% of men with KS redeemed prescriptions for testosterone. Untreated men with KS were on average born 12 years before those treated, and the majority of untreated men with KS with available biochemistry were hypogonadal. Testosterone treatment in KS was associated with a non-significant decrease in venous thromboembolism and thrombotic deaths.

CONCLUSION

Thrombosis and thrombotic deaths are increased in KS. Only half of the men with KS ever received testosterone treatment, despite overt hypogonadism in the non-treated. Testosterone treatment in Klinefelter syndrome was insignificantly associated with lower incidence rates of venous thrombosis and thrombotic deaths.

Single-Cell Sequencing Reveals the Relationship between Phenotypes and Genotypes of Klinefelter Syndrome

Klinefelter syndrome (KS) is one of the most common congenital disorders of male infertility. Given its high heterogeneity in clinical and genetic presentation, the relationship between transcriptome, clinical phenotype, and associated co-morbidities seen in KS has not been fully clarified. Here, we report a 47,XXY Chinese male with infertility and analyzed the differences in gene expression patterns of peripheral blood mononuclear cells (PBMCs) with regard to a Chinese male and a female control with normal karyotype by single-cell sequencing. A total of 24,439 cells were analyzed and divided into 5 immune cell types (including B cells, T cells, macrophage cells, dendritic cells, and natural killer cells) according to marker genes. Using unsupervised dimensionality reduction and clustering algorithms, we identified molecularly distinct subpopulations of cells between the KS patient and both controls. Gene ontology enrichment analyses yielded terms associated with well-known comorbidities seen in KS as well as an affected immune system and type I diabetes mellitus. Based on our data, we identified several candidate genes which may be implicated in regulating the phenotype of KS. Overall, this analysis provides a comprehensive map of the cell types of PBMCs in a KS patient at the single-cell level, which will contribute to the prevention of comorbidity and improvement of the life quality of KS patients.

Mortality in 43,598 men with infertility - a Swedish nationwide population-based cohort study

Background

Previous studies indicate a higher risk of comorbidity in men with infertility; however, research on mortality is scarce and the few studies that do exist have rarely differentiated between infertility and infertility-related diagnoses.

Objective

To examine mortality in men with an infertility or infertility-related diagnosis.

Design, setting, and participants

Population-based cohort study of men born in 1944–1992 in Sweden. We used Cox regression estimated hazard ratios (HRs) for infertility while adjusting for number of children, education, year of birth, country of birth, diabetes, hypertension, liver disease and end-stage renal disease. In all, 43,598 men with a diagnosis of infertility and 57,733 men with an infertility-related diagnosis were compared with 2,762,254 men (reference group) without such diagnoses.

Outcome measures

All-cause and cause-specific mortality at age 20 to 69 years.

Results and limitations

The 2,863,585 men in the study were followed for a median time of 22.0 years. During follow-up, 439 men with a diagnosis of infertility died, corresponding to a crude incidence rate of 1.56 deaths per 1,000 person-years. These figures can be compared with 1,400 deaths in men with an infertility-related diagnosis (1.96 deaths/1,000 person-years) and 99,463 deaths in reference individuals (2.17 deaths/1,000 person-years). Overall, men with a diagnosis of infertility did not have a higher risk of death (adjusted [a]HR=0.98; 95% confidence interval [95% CI]=0.89–1.08), but had a higher risk of death before age 30 (20–29 years) (aHR=3.26; 95% CI=2.42–4.41). This early excess mortality was largely explained by cancer diagnosed before infertility. Having an infertility-related diagnosis was associated with death (aHR=1.23; 95% CI=1.17–1.30). Limitations include the lack of general screening for infertility in Sweden and the lack of information on semen parameters.

Conclusion

Men with a diagnosis of infertility are not at a higher risk of death than the general population, although having a diagnosis related to infertility may be linked to a higher risk of death.

Patient summary

Men with a diagnosis of infertility do not seem to have a higher risk of death though an infertility-related diagnosis in men is associated with the risk of death.

Klinefelter syndrome: From pediatrics to geriatrics

BACKGROUND

Klinefelter syndrome (KS) is one of the major causes of nonobstructive azoospermia (NOA). Microdissection testicular sperm extraction (micro-TESE) is often performed to retrieve sperm. Infertility specialists have to care for KS patients on a lifelong basis.

METHODS

Based on a literature review and our own experience, male infertility treatment and KS pathophysiology were considered on a lifelong basis.

MAIN FINDINGS

Patients diagnosed early often have an increased number of aberrant X chromosomes. Cryptorchidism and hypospadias are often found, and surgical correction is required. Cryopreservation of testicular sperm during adolescence is an issue of debate because the sperm retrieval rate (SRR) in KS patients decreases with age. The SRR in adult KS patients is higher than that in other patients with NOA; however, low testosterone levels after micro-TESE will lower the general health and quality of life. KS men face a number of comorbidities, such as malignancies, metabolic syndrome, diabetes, cardiovascular disease, bone disease, and immune diseases, which ultimately results in increased mortality rates.

CONCLUSION

A deeper understanding of the pathophysiology of KS and the histories of KS patients before they seek infertility treatment, during which discussions with multidisciplinary teams are sometimes needed, will help to properly treat these patients.

Management of cardiovascular complications in Klinefelter syndrome patients

INTRODUCTION

Klinefelter syndrome (KS), also known as 47, XXY, shows increased mortality when compared with mortality rates among the general population. Cardiovascular, hemostatic, metabolic diseases are implicated. Moreover, cardiac congenital anomalies in KS can contribute to the increase in mortality.

AREAS COVERED

In this study, we have systematically reviewed the relationships between KS and the cardiovascular system and the management of cardiovascular complication. In summary, patients with KS display increased cardiovascular risk profile, characterized by increased prevalence of metabolic alterations including dyslipidemia, diabetes mellitus (DM), and abnormalities in biomarkers of cardiovascular disease. KS subjects are characterized by subclinical abnormalities in endothelial function and in left ventricular (LV) systolic and diastolic function, which - when associated with chronotropic incompetence - may negatively influence cardiopulmonary performance. Moreover, KS patients appear to be at a higher risk for cardiovascular disease, due to thromboembolic events with high prevalence of recurrent venous ulcers, venous insufficiency, recurrent venous and arterial thromboembolism leading to deep venous thrombosis or pulmonary embolism.

EXPERT OPINION

Considering the unequivocal finding of increased mortality of KS patients, we suggest a periodic cardiovascular follow up in specialized centers with multidisciplinary care teams that comprise endocrinologists and cardiologists dedicated to KS syndrome.

Changes in the cohort composition of turner syndrome and severe non-diagnosis of Klinefelter, 47,XXX and 47,XYY syndrome: a nationwide cohort study

Background

Knowledge on the prevalence of sex chromosome abnormalities (SCAs) is limited, and delayed diagnosis or non-diagnosis of SCAs are a continuous concern. We aimed to investigate change over time in incidence, prevalence and age at diagnosis among Turner syndrome (TS), Klinefelter syndrome (KS), Triple X syndrome (Triple X) and Double Y syndrome (Double Y).

Methods

This study is a nationwide cohort study in a public health care system. The Danish Cytogenetic Central Registry (DCCR) holds information on all karyotypes performed in Denmark since 1961. We identified all individuals in the DCCR with a relevant SCA during 1961–2014; TS: n = 1156; KS: n = 1235; Triple X: n = 197; and Double Y: n = 287. From Statistics Denmark, which holds an extensive collection of data on the Danish population, complete data concerning dates of death and migrations in and out of Denmark were retrieved for all individuals.

Results

The prevalence among newborns was as follows: TS: 59 per 100,000 females; KS: 57 per 100,000 males; Triple X: 11 per 100,000 females; and Double Y: 18 per 100,000 males. Compared with the expected number among newborns, all TS, 38% of KS, 13% of Triple X, and 18% of Double Y did eventually receive a diagnosis. The incidence of TS with other karyotypes than 45,X (P < 0.0001), KS (P = 0.02), and Double Y (P = 0.03) increased during the study period whereas the incidence of 45,X TS decreased (P = 0.0006). The incidence of Triple X was stable (P = 0.22).

Conclusions

The prevalence of TS is higher than previously identified, and the karyotypic composition of the TS population is changing. Non-diagnosis is extensive among KS, Triple X and Double Y, whereas all TS seem to become diagnosed. The diagnostic activity has increased among TS with other karyotypes than 45,X as well as among KS and Double Y.

New Biomarkers to Evaluate Hyperandrogenemic Women and Hypogonadal Men

Androgens can have variable effects on men and women. Women may be evaluated for androgen excess for several reasons. Typically, young premenopausal women present with clinical symptoms of hirsutism, alopecia, irregular menses, and/or infertility. The most common cause of these symptoms is polycystic ovary syndrome. After menopause, even though ovaries stop producing estrogen, they continue to produce androgen, and women can have new onset of hirsutism and alopecia. Laboratory evaluation involves measurement of the major ovarian and adrenal androgens. In women, age, phase of the menstrual cycle, menopausal status, obesity, metabolic health, and sex hormone-binding proteins significantly affect total-androgen levels and complicate interpretation. This review will summarize the clinically relevant evaluation of hyperandrogenemia at different life stages in women and highlight pitfalls associated with interpretation of commonly used hormone measurements. Hypogonadism in men is a clinical syndrome characterized by low testosterone and/or low sperm count. Symptoms of hypogonadism include decreased libido, erectile dysfunction, decreased vitality, decreased muscle mass, increased adiposity, depressed mood, osteopenia, and osteoporosis. Hypogonadism is a common disorder in aging men. Hypogonadism is observed rarely in young boys and adolescent men. Based on the defects in testes, hypothalamus, and/or pituitary glands, hypogonadism can be broadly classified as primary, secondary, and mixed hypogonadism. Diagnosis of hypogonadism in men is based on symptoms and laboratory measurement. Biomarkers in use/development for hypogonadism are classified as hormonal, Leydig and Sertoli cell function, semen, genetic/RNA, metabolic, microbiome, and muscle mass-related. These biomarkers are useful for diagnosis of hypogonadism, determination of the type of hypogonadism, identification of the underlying causes, and therapeutic assessment. Measurement of serum testosterone is usually the most important single diagnostic test for male hypogonadism. Patients with primary hypogonadism have low testosterone and increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Patients with secondary hypogonadism have low testosterone and low or inappropriately normal LH and FSH. This review provides an overview of hypogonadism in men and a detailed discussion of biomarkers currently in use and in development for diagnosis thereof.

Klinefelter syndrome, insulin resistance, metabolic syndrome, and diabetes: review of literature and clinical perspectives

PURPOSE

Klinefelter syndrome (KS), the most frequent chromosomic abnormality in males, is associated with hypergonadotropic hypogonadism and an increased risk of cardiovascular diseases (CVD). The mechanisms involved in increasing risk of cardiovascular morbidity and mortality are not completely understood. This review summarises the current understandings of the complex relationship between KS, metabolic syndrome and cardiovascular risk in order to plan future studies and improve current strategies to reduce mortality in this high-risk population.

METHODS

We searched PubMed, Web of Science, and Scopus for manuscripts published prior to November 2017 using key words "Klinefelter syndrome" AND "insulin resistance" OR "metabolic syndrome" OR "diabetes mellitus" OR "cardiovascular disease" OR "testosterone". Manuscripts were collated, studied and carried forward for discussion where appropriate.

RESULTS

Insulin resistance, metabolic syndrome, and type 2 diabetes are more frequently diagnosed in KS than in the general population; however, the contribution of hypogonadism to metabolic derangement is highly controversial. Whether this dangerous combination of risk factors fully explains the CVD burden of KS patients remains unclear. In addition, testosterone replacement therapy only exerts a marginal action on the CVD system.

CONCLUSION

Since fat accumulation and distribution seem to play a relevant role in triggering metabolic abnormalities, an early diagnosis and a tailored intervention strategy with drugs aimed at targeting excessive visceral fat deposition appear necessary in patients with KS.

Novel insights on testicular volume and testosterone replacement therapy in Klinefelter patients undergoing testicular sperm extraction. A retrospective clinical study

STUDY QUESTION

To investigate whether sperm recovery is related to clinical features, hormone parameters and testosterone replacement therapy (TRT) in patients with Klinefelter syndrome (KS).

SUMMARY ANSWER

This study provides three interesting insights: (i) the probability to retrieve sperm is not related to testicular volume; (ii) TRT does not affect sperm retrieval rate (SRR); and (iii) reduced levels of LH and FSH represent a negative predictor of sperm retrieval in patients with TRT.

WHAT IS KNOWN ALREADY

Classical KS shows a karyotype with one extra X chromosome in all of somatic cells and clinical manifestations characterized by hypergonadotropic hypogonadism and infertility.

STUDY DESIGN, SIZE AND DURATION

We performed a retrospective cohort study. Data from 111 consecutive KS azoospermic patients undergoing testicular sperm extraction (TESE) were collected from 2005 to 2016.

PARTICIPANTS/MATERIALS, SETTING AND METHODS

Data on anthropometric parameters, reproductive hormones and testicular volumes were collected. SRR was related to clinical characteristics and compared between TRT and untreated patients.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 38 patients (34.2%) had successful sperm recovery. The comparison of clinical characteristics did not differ between patients with and without sperm recovery. Sperm retrieval was successful also in subjects with smaller testes. The comparison of SRR in patients with or without TRT was not different (33.3% vs 34.6%). In TRT group, LH and FSH levels were significantly lower in subjects with no sperm retrieval (P values, respectively, <.05 and <.001).

LIMITATIONS AND REASONS FOR CAUTION

Well-designed controlled studies are necessary to confirm these data aimed to set the best therapeutic approach for fertility management in hypogonadal patients with nonmosaic KS.

WIDER IMPLICATIONS OF THE FINDINGS

Age at TESE, anthropometric measures, testis volume, sex hormones levels and semen parameters are not predictive parameters of SRR. Among TRT patients, reduced gonadotropin is related to failure in sperm retrieval.

Hypogonadism Makes Dyslipidemia in Klinefelter's Syndrome

Klinefelter's syndrome (KS) is a genetic syndrome that presents with hypogonadism and is associated with metabolic syndrome. Patients demonstrating hypogonadism show a greater prevalence of metabolic syndrome due to changes in body composition. We aimed to determine the association between KS and dyslipidemia. The KS group comprised 55 patients who visited the infertility clinic for an infertility evaluation and were confirmed as having a diagnosis of KS. The control group comprised 120 patients who visited the clinic for health screening. Patient characteristics were compared between the two groups with respect to height, weight, body mass index (BMI), testosterone, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and triglyceride (TG) levels. Height and weight were significantly greater in patients belonging to the KS group, but no statistically significant difference was found with respect to the BMI. Testosterone levels in patients belonging to the KS group were significantly lower compared to the control group (2.4 ± 2.6 vs. 5.2 ± 1.8 ng/mL, P < 0.001). Compared to the control group, TG levels in patients belonging to the KS group were increased (134.9 ± 127.8 vs. 187.9 ± 192.1 mg/dL, P = 0.004) and HDL cholesterol was significantly decreased (51.2 ± 22.0 vs. 44.0 ± 9.5 mg/dL, P = 0.009). LDL cholesterol and total cholesterol were not significantly different between the two groups (P = 0.076 and P = 0.256, respectively). Significant differences were noted between patients belonging to the KS group and normal control group with respect to elevated TG and decreased HDL cholesterol levels.

Aberrant ocular architecture and function in patients with Klinefelter syndrome

Klinefelter Syndrome (KS), the most common chromosomal disorder in men (47,XXY), is associated with numerous comorbidities. Based on a number of isolated case reports, we performed the first systematic and comprehensive evaluation of eye health in KS patients with a focus on ocular structure and vascularization. Twenty-one KS patients and 26 male and 38 female controls underwent a variety of non-invasive examinations investigating ocular morphology (examination of retinal thickness, optic nerve head, and cornea) and function (visual field testing and quantification of ocular vessel density by optical coherence tomography angiography). In comparison to healthy controls, KS patients exhibited a smaller foveal avascular zone and a decreased retinal thickness due to a drastically thinner outer nuclear layer. The cornea of KS patients showed a decreased peripheral thickness and volume. In perimetry evaluation, KS patients required brighter stimuli and gave more irregular values. KS patients show an ocular phenotype including morphological and functional features, which is very likely caused by the supernumerary X chromosome. Thus, KS should not be limited to infertility, endocrine dysfunction, neurocognitive and psychosocial comorbidities. Defining an aberrant ocular morphology and function, awareness for possible eye problems should be raised.

Long-term follow-up of a child with Klinefelter syndrome and achondroplasia from infancy to 16 years

BACKGROUND

Achondroplasia (ACH), an autosomal dominant skeletal dysplasia, occurs in approximately 1:20,000 births. On the other hand, 47,XXY aneuploidy (Klinefelter syndrome [KS]) is the most common sex chromosome disorder, with a prevalence of approximately 1:600 males. To the best of our knowledge, only five cases of patients presenting both ACH and KS have been reported to date in the international literature. However, none of these cases has been longitudinally followed during the entire childhood.

CASE PRESENTATION

We report a male patient with ACH and KS, diagnosed in early infancy because of his typical phenotype of ACH. The diagnosis was confirmed by molecular analysis revealing a de novo heterozygous 1138 G-to-A mutation of the FGFR3 gene. During his first assessment, a karyotype was performed, which also revealed coexistence of KS. He was followed by our pediatric endocrinology team until the age of 16 years, then he was gradually transferred to adult endocrine care.

CONCLUSIONS

This is the first reported case with both conditions that was diagnosed in infancy and was longitudinally followed by a pediatric endocrinology team regularly, from infancy to late adolescence. With a typical phenotype of ACH, it is striking and noteworthy that he did not develop the classical endocrine complications of a child with KS, neither did he necessitate testosterone supplementation during his pubertal development, due to his normal virilization and testosterone levels.

Klinefelter syndrome: cardiovascular abnormalities and metabolic disorders

Klinefelter syndrome (KS) is one of the most common genetic causes of male infertility. This condition is associated with much comorbidity and with a lower life expectancy. The aim of this review is to explore more in depth cardiovascular and metabolic disorders associated to KS. KS patients have an increased risk of cerebrovascular disease (standardized mortality ratio, SMR, 2.2; 95% confidence interval, CI, 1.6-3.0), but it is not clear whether the cause of the death is of thrombotic or hemorrhagic nature. Cardiovascular congenital anomalies (SMR, 7.3; 95% CI, 2.4-17.1) and the development of thrombosis or leg ulcers (SMR, 7.9; 95% CI, 2.9-17.2) are also more frequent in these subjects. Moreover, cardiovascular abnormalities may be at least partially reversed by testosterone replacement therapy (TRT). KS patients have also an increased probability of endocrine and/or metabolic disease, especially obesity, metabolic syndrome and type 2 diabetes mellitus. The effects of TRT on these abnormalities are not entirely clear.

Dihydrotestosterone: Biochemistry, Physiology, and Clinical Implications of Elevated Blood Levels

Benefits associated with lowered serum DHT levels after 5α-reductase inhibitor (5AR-I) therapy in men have contributed to a misconception that circulating DHT levels are an important stimulus for androgenic action in target tissues (e.g., prostate). Yet evidence from clinical studies indicates that intracellular concentrations of androgens (particularly in androgen-sensitive tissues) are essentially independent of circulating levels. To assess the clinical significance of modest elevations in serum DHT and the DHT/testosterone (T) ratio observed in response to common T replacement therapy, a comprehensive review of the published literature was performed to identify relevant data. Although the primary focus of this review is about DHT in men, we also provide a brief overview of DHT in women. The available published data are limited by the lack of large, well-controlled studies of long duration that are sufficiently powered to expose subtle safety signals. Nonetheless, the preponderance of available clinical data indicates that modest elevations in circulating levels of DHT in response to androgen therapy should not be of concern in clinical practice. Elevated DHT has not been associated with increased risk of prostate disease (e.g., cancer or benign hyperplasia) nor does it appear to have any systemic effects on cardiovascular disease safety parameters (including increased risk of polycythemia) beyond those commonly observed with available T preparations. Well-controlled, long-term studies of transdermal DHT preparations have failed to identify safety signals unique to markedly elevated circulating DHT concentrations or signals materially different from T.

Klinefelter syndrome comorbidities linked to increased X chromosome gene dosage and altered protein interactome activity

Klinefelter syndrome (KS) (47,XXY) is the most common male sex chromosome aneuploidy. Diagnosis and clinical supervision remain a challenge due to varying phenotypic presentation and insufficient characterization of the syndrome. Here we combine health data-driven epidemiology and molecular level systems biology to improve the understanding of KS and the molecular interplay influencing its comorbidities. In total, 78 overrepresented KS comorbidities were identified using in- and out-patient registry data from the entire Danish population covering 6.8 million individuals. The comorbidities extracted included both clinically well-known (e.g. infertility and osteoporosis) and still less established KS comorbidities (e.g. pituitary gland hypofunction and dental caries). Several systems biology approaches were applied to identify key molecular players underlying KS comorbidities: Identification of co-expressed modules as well as central hubs and gene dosage perturbed protein complexes in a KS comorbidity network build from known disease proteins and their protein–protein interactions. The systems biology approaches together pointed to novel aspects of KS disease phenotypes including perturbed Jak-STAT pathway, dysregulated genes important for disturbed immune system (IL4), energy balance (POMC and LEP) and erythropoietin signalling in KS. We present an extended epidemiological study that links KS comorbidities to the molecular level and identify potential causal players in the disease biology underlying the identified comorbidities.

Klinefelter syndrome (KS): genetics, clinical phenotype and hypogonadism

Klinefelter Syndrome (KS) is characterized by an extreme heterogeneity in its clinical and genetic presentation. The relationship between clinical phenotype and genetic background has been partially disclosed; nevertheless, physicians are aware that several aspects concerning this issue are far to be fully understood. By improving our knowledge on the role of some genetic aspects as well as on the KS, patients' interindividual differences in terms of health status will result in a better management of this chromosomal disease. The aim of this review is to provide an update on both genetic and clinical phenotype and their interrelationships.

Effects of Oxandrolone on Cardiometabolic Health in Boys With Klinefelter Syndrome: A Randomized Controlled Trial

CONTEXT

Klinefelter syndrome (KS) is a common condition in males, resulting in androgen deficiency and cardiometabolic diseases. These interrelated conditions may be present in prepubertal boys with KS.

OBJECTIVE

To determine whether supplemental low-dose androgen has a beneficial effect on body composition in prepubertal boys with KS.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a secondary analysis of a randomized, double-blind, placebo-controlled clinical trial in 93 boys with KS aged 4 to 12 years.

INTERVENTIONS

Oral oxandrolone (Ox) 0.06 mg/kg/d or placebo for 2 years.

OUTCOME MEASURES

The primary outcome was percent body fat standard deviation score (%BF SDS) at 2 years. Secondary outcomes included additional measures of cardiometabolic health and safety.

RESULTS

The %BF SDS at 2 years was significantly lower in the treatment (0.29 ± 0.76 SDS) compared with placebo group (0.81 ± 0.72 SDS) after adjusting for age and baseline %BF SDS (95% confidence interval for the difference between means -0.86 to -0.19 SDS, P = 0.009). Ox resulted in lower triglycerides (P = 0.043), but also lower high-density lipoprotein (HDL) cholesterol (P < 0.001) and a more rapid advancement in bone age (P = 0.011).

CONCLUSIONS

Ox has positive effects on measures of cardiometabolic health in prepubertal boys with KS; however, it does lower HDL cholesterol and advance bone age.

Thrombophilia in Klinefelter Syndrome With Deep Venous Thrombosis, Pulmonary Embolism, and Mesenteric Artery Thrombosis on Testosterone Therapy: A Pilot Study

We compared thrombophilia and hypofibrinolysis in 6 men with Klinefelter syndrome (KS), without previously known familial thrombophilia, who had sustained deep venous thrombosis (DVT)-pulmonary emboli (PE) or mesenteric artery thrombosis on testosterone replacement therapy (TRT). After the diagnosis of KS, TRT had been started in the 6 men at ages 11, 12, 13, 13, 19, and 48 years. After starting TRT, DVT-PE or mesenteric artery thrombosis was developed in 6 months, 1, 11, 11, 12, and 49 years. Of the 6 men, 4 had high (>150%) factor VIII (177%, 192%, 263%, and 293%), 3 had high (>150%) factor XI (165%, 181%, and 193%), 1 was heterozygous for the factor V Leiden mutation, and 1 was heterozygous for the G20210A prothrombin gene mutation. None of the 6 men had a precipitating event before their DVT-PE. We speculate that the previously known increased rate of DVT-PE and other thrombi in KS reflects an interaction between prothrombotic, long-term TRT with previously undiagnosed familial thrombophilia. Thrombophilia screening in men with KS before starting TRT would identify a cohort at increased risk for subsequent DVT-PE, providing an optimally informed estimate of the risk/benefit ratio of TRT.

Anatomical and clinical aspects of Klinefelter's syndrome

Klinefelter's syndrome, the most common sex disorder associated with chromosomal aberrations, is characterized by a plethora of clinical features. Parameters for diagnosis of the syndrome are constantly expanding as new anatomical and hormonal abnormalities are noted, yet Klinefelter's remains underdiagnosed and underreported. This review outlines the key anatomical characteristics associated with the syndrome, which are currently used for clinical diagnosis, or may provide means for improving diagnosis in the future. Clin. Anat. 29:606-619, 2016. © 2016 Wiley Periodicals, Inc.

The importance of having two X chromosomes

Historically, it was thought that the number of X chromosomes plays little role in causing sex differences in traits. Recently, selected mouse models have been used increasingly to compare mice with the same type of gonad but with one versus two copies of the X chromosome. Study of these models demonstrates that mice with one X chromosome can be strikingly different from those with two X chromosomes, when the differences are not attributable to confounding group differences in gonadal hormones. The number of X chromosomes affects adiposity and metabolic disease, cardiovascular ischaemia/reperfusion injury and behaviour. The effects of X chromosome number are likely the result of inherent differences in expression of X genes that escape inactivation, and are therefore expressed from both X chromosomes in XX mice, resulting in a higher level of expression when two X chromosomes are present. The effects of X chromosome number contribute to sex differences in disease phenotypes, and may explain some features of X chromosome aneuploidies such as in Turner and Klinefelter syndromes.

Phenotype and Adverse Quality of Life in Boys with Klinefelter Syndrome

OBJECTIVES

To characterize associations among psychosocial well-being, physical phenotype, and sex hormones in a sample of youth with Klinefelter syndrome (KS). We hypothesized that KS physical traits (phenotype) are associated with adverse psychosocial health measures and that testosterone levels are associated with adverse psychosocial health.

STUDY DESIGN

Forty-three boys with KS (ages 8-18 years) participated in a cross-sectional study. Participants underwent physical examination, hormone analyses, and psychosocial health questionnaires.

RESULTS

Using an investigator-developed Klinefelter Phenotype Index Scale, the number of KS physical traits ranged from 1-13 (mean 5.1 ± 1.9). Pubertal boys presented with more KS traits compared with prepubertal boys (5.6 vs 4.2, P = .01). Boys diagnosed prenatally had a milder phenotype compared with those diagnosed postnatally. Gonadotropins were elevated without androgen deficiency in 45%. Psychosocial health scores indicated adverse quality of life (QOL) (67%), low self-esteem (38%), poor self-concept (26%), and risk for depression (16%) without a difference between pubertal groups. Linear regression showed that 22% of the variance in QOL (P = .0001) was explained by phenotype. Testosterone level was not associated with psychosocial health measures.

CONCLUSIONS

Depending on the degree of phenotypic abnormality, boys with KS may be at risk for impaired QOL. Testosterone levels were not shown to influence psychosocial health. The Klinefelter Phenotype Index Scale may be a useful tool to characterize KS features in boys.

Role of vitamin D levels and vitamin D supplementation on bone mineral density in Klinefelter syndrome

This manuscript describes the role of low vitamin D in bone metabolism of Klinefelter subjects. Low vitamin D is frequent in this condition and seems to be more important than testosterone in inducing low bone mineral density (BMD) and osteoporosis. Supplementation with vitamin D restores BMD after 2 years of treatment, whereas testosterone alone seems to be ineffective.

INTRODUCTION

Decreased bone mineral density (BMD) in Klinefelter syndrome (KS) is frequent, and it has been traditionally related to low testosterone (T) levels. However, low BMD can be observed also in patients with normal T levels and T replacement therapy does not necessarily increase bone mass in these patients. Nothing is known about vitamin D levels and supplementation in KS. In this study, we determine vitamin D status and bone mass in KS subjects and compare the efficacy of T therapy and vitamin D supplementation on BMD.

METHODS

A total of 127 non-mosaic KS patients and 60 age-matched male controls were evaluated with reproductive hormones, 25-hydroxyvitamin D, PTH, and bone densitometry by dual-energy X-ray absorptiometry (DEXA). Patients with hypogonadism and/or 25-hydroxyvitamin D deficiency were treated with T-gel 2% and/or calcifediol and re-evaluated after 24 months of treatment.

RESULTS

25-hydroxyvitamin D levels were significantly lower in KS patients with respect to controls, and they had significantly lower lumbar and femoral BMD. The percentage of osteopenia/osteoporosis in subjects with 25-hydroxyvitamin D deficiency was higher with respect to subjects with normal 25-hydroxyvitamin D and was not related to the presence/absence of low T levels. Subjects treated with calcifediol or T + calcifediol had a significant increase in lumbar BMD after treatment. No difference was found in T-treated group.

CONCLUSIONS

These data highlight that low 25-hydroxyvitamin D levels seem to have a more critical role than low T levels in inducing low BMD in KS subjects. Furthermore, vitamin D supplementation seems to be more effective than T replacement therapy alone in increasing BMD.

Factors associated with adaptation to Klinefelter syndrome: the experience of adolescents and adults

OBJECTIVE

The purpose of this study was to understand the impact of living with Klinefelter syndrome (XXY) as an adolescent or an adult and to examine the factors that contribute to adaptation.

METHODS

Individuals (n = 310) aged 14-75 years with self-reported XXY were recruited from online support networks to complete a self-administered survey. Perceived consequences, perceived severity, perceived stigma, and coping were measured and evaluated as correlates of adaptation.

RESULTS

The use of problem-focused coping strategies was positively correlated with adaptation (p < 0.01) and age was negatively correlated with adaptation (p < 0.05).

CONCLUSION

The majority of participants reported significant negative consequences of XXY, including infertility, psychological co-morbidities and differences in appearance. How participants coped with their negative appraisals was the greatest predictor of adaptation.

PRACTICE IMPLICATIONS

Interventions designed to help individuals reframe negative appraisals, to increase perceived manageability of the challenges of living with XXY, and to facilitate effective coping may improve adaptation among individuals with XXY.