Gonadal function is associated with cardiometabolic health in pre-pubertal boys with Klinefelter syndrome

Hormone Therapy During Infancy or Early Childhood for Patients with Hypogonadotropic Hypogonadism, Klinefelter or Turner Syndrome: Has the Time Come?

Managing patients unable to produce sex steroids using gonadotropins to mimic minipuberty in hypogonadotropic hypogonadism, or sex steroids in patients with Klinefelter or Turner syndrome, is promising. There is a need to pursue research in this area, with large prospective cohorts and long-term data before these treatments can be routinely considered.

Serum Lipocalin-2 Levels as a Biomarker in Pre- and Post-Pubertal Klinefelter Syndrome Patients: A Pilot Study

Klinefelter syndrome (KS) is a male genetic disease caused by the presence of an extra X chromosome, causing endocrine disorders mainly responsible for a high rate of infertility and metabolic disorders in adulthood. Scientific research is interested in identifying new biomarkers that can be predictive or prognostic of alterations strictly connected to KS. Lipocalin-2 (LCN-2, also known as NGAL) is a small protein initially identified within neutrophils as a protein related to innate immunity. Serum LCN-2 estimation seems to be a useful tool in predicting the metabolic complications caused by several pathological conditions. However, little is known about its potential role in infertility conditions. The present pilot study aims to investigate the presence of LCN-2 in the serum of a group of pre-pubertal and post-pubertal children affected by KS, compared to healthy controls. We demonstrated for the first time the presence of elevated levels of LCN-2 in the serum of KS patients, compared to controls. This increase was accompanied, in pre-pubertal KS patients, by the loss of correlation with LH and HDL, which instead was present in the healthy individuals. Moreover, in all KS individuals, a positive correlation between LCN-2 and inhibin B serum concentration was found. Despite the limited size of the sample analyzed, our preliminary data encourage further studies to confirm the findings and to extend the study to KS adult patients, to verify the predictive/prognostic value of LCN-2 as new biomarker for metabolic diseases and infertility associated with the pathology.

Reproductive hormones, bone mineral content, body composition, and testosterone therapy in boys and adolescents with Klinefelter syndrome

Adult patients with Klinefelter syndrome (KS) are characterized by a highly variable phenotype, including tall stature, obesity, and hypergonadotropic hypogonadism, as well as an increased risk of developing insulin resistance, metabolic syndrome, and osteoporosis. Most adults need testosterone replacement therapy (TRT), whereas the use of TRT during puberty has been debated. In this retrospective, observational study, reproductive hormones and whole-body dual-energy x-ray absorptiometry-derived body composition and bone mineral content were standardized to age-related standard deviation scores in 62 patients with KS aged 5.9-20.6 years. Serum concentrations of total testosterone and inhibin B were low, whereas luteinizing hormone and follicle-stimulating hormone were high in patients before TRT. Despite normal body mass index, body fat percentage and the ratio between android fat percentage and gynoid fat percentage were significantly higher in the entire group irrespective of treatment status. In patients evaluated before and during TRT, a tendency toward a more beneficial body composition with a significant reduction in the ratio between android fat percentage and gynoid fat percentage during TRT was found. Bone mineral content (BMC) did not differ from the reference, but BMC corrected for bone area was significantly lower when compared to the reference. This study confirms that patients with KS have an unfavorable body composition and an impaired bone mineral status already during childhood and adolescence. Systematic studies are needed to evaluate whether TRT during puberty will improve these parameters.

The complications of male hypogonadism: is it just a matter of low testosterone?

The history of diagnosing hypogonadism and hypotestosteronemia shows us the many steps that were necessary to achieve our current knowledge and the ability to improve these patients' well-being. Moreover, so far, criteria for diagnosing hypotestosteronemia varies according to the underlying condition, and according to the consensus or guideline adopted. Furthermore, besides the many signs and symptoms, there are several complications associated with low testosterone levels such as osteoporosis, metabolic alterations, as well as cardiovascular disorders. However, data are often conflicting regarding the severity, timing or even the real clinical relevance of these complications, although these studies often lack essential information such as gonadotropin levels or the underlying cause of hypogonadism. The present review focus on the complications of male hypogonadism according to the cause of testosterone deficiency, highlighting the lack of information found in many studies investigating its effects. We thereby stress the necessity to always perform a complete evaluation of the type of hypogonadism (including at least gonadotropins and secondary causes) when investigating the effects of low testosterone levels.

Biochemical identification of prepubertal boys with Klinefelter syndrome by combined reproductive hormone profiling using machine learning

Objective

Klinefelter syndrome (KS) is the most common sex chromosome disorder and genetic cause of infertility in males. A highly variable phenotype contributes to the fact that a large proportion of cases are never diagnosed. Typical hallmarks in adults include small testes and azoospermia which may prompt biochemical evaluation that typically shows extremely high follicle-stimulating hormone and low/undetectable inhibin B serum concentrations. However, in prepubertal KS individuals, biochemical parameters are largely overlapping those of prepubertal controls. We aimed to characterize clinical profiles of prepubertal boys with KS in relation to controls and to develop a novel biochemical classification model to identify KS before puberty.

Methods

Retrospective, longitudinal data from 15 prepubertal boys with KS and data from 1475 controls were used to calculate age- and sex-adjusted standard deviation scores (SDS) for height and serum concentrations of reproductive hormones and used to infer a decision tree classification model for KS.

Results

Individual reproductive hormones were low but within reference ranges and did not discriminate KS from controls. Clinical and biochemical profiles including age- and sex-adjusted SDS from multiple reference curves provided input data to train a 'random forest' machine learning (ML) model for the detection of KS. Applied to unseen data, the ML model achieved a classification accuracy of 78% (95% CI, 61-94%).

Conclusions

Supervised ML applied to clinically relevant variables enabled computational classification of control and KS profiles. The application of age- and sex-adjusted SDS provided robust predictions irrespective of age. Specialized ML models applied to combined reproductive hormone concentrations may be useful diagnostic tools to improve the identification of prepubertal boys with KS.

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.

Lower Circulating Sertoli and Leydig Cell Hormone Levels During Puberty in Obese Boys: A Cross-sectional Study

CONTEXT

Alterations in semen characteristics and circulating Sertoli and Leydig cell hormones have been described in obese male adults. Whether hormonal alterations occur before adulthood has not been fully evaluated.

OBJECTIVE

We describe circulating Sertoli and Leydig cell hormone levels in overweight-obese (ow/ob) boys through childhood and adolescence in a cross-sectional study.

METHODS

Monocentric study in the Pediatric Endocrinology Unit of Angers University Hospital. Three hundred and fifty-one obese and overweight boys aged 5-19 years underwent physical examination, dual-energy X-ray absorptiometry for body composition, oral glucose tolerance test on insulin and glucose, and measurements of follicle-stimulating hormone, luteinizing hormone, anti-Müllerian hormone (AMH), inhibin B, testosterone, and estradiol. Hormonal levels were compared with normative data obtained from 652 healthy nonoverweight nonobese boys of similar age or Tanner stage.

RESULTS

Median inhibin B and testosterone levels during puberty were significantly lower in ow/ob than in healthy boys (1) from age >12 years and thereafter for inhibin B, and (2) from age >14 years and thereafter for testosterone. At Tanner stages 4 and 5, 26%, 31%, and 18% of inhibin B, testosterone, and AMH values were below the 5th percentile in ow/ob subjects (P < .01). In multiple regression analyses, estradiol and total bone mineral density Z-score were negative predictors of inhibin B, fat mass percentage was a negative predictor of testosterone, and insulin was a negative predictor of AMH.

CONCLUSION

Lower Sertoli and Leydig cell hormone levels during puberty were observed in the ow/ob boys.

Onset and progression of puberty in Klinefelter syndrome

OBJECTIVE

Klinefelter syndrome (KS) (47,XXY and variants, KS) is the most common sex chromosome disorder in humans. However, little is known about the onset and progression of puberty in patients with KS. In this study, we describe the onset and progression of puberty in a large series of boys with KS in a single tertiary centre.

DESIGN AND PATIENTS

Retrospective data (Tanner stages, testicular length, testosterone supplementation, levels of luteinizing hormone [LH] and testosterone) before possible testosterone treatment on 72 KS patients with 47,XXY karyotype were reviewed, and G (n = 59 patients) and P (n = 56 patients) stages were plotted on puberty nomograms.

MEASUREMENTS AND RESULTS

One boy had a delayed onset of puberty, as he was at the G1 stage at the age of 13.8 years (-2.2 SDs). No observations of delay were made of boys at Stage G2. The progression of G stages was within normal limits in the majority of patients; only few boys were late at G3 (4.1%; 1 out of 24) and G4 (7.4%; 2 out of 27). Testosterone supplementation was started at the average age of 15.5 years to 35 boys (47%), 2 of whom were over 18 years old. LH level was on average 18.2 IU/L (SD: 6.3 IU/L) and testosterone 9.1 nmol/L (SD: 3.1 nmol/L) when testosterone supplementation was started.

CONCLUSIONS

Our results suggest that puberty starts within the normal age limits in boys with KS, and testosterone supplementation is not needed for the initial pubertal progression in the majority of patients.

Glucose metabolic disorder in Klinefelter syndrome: a retrospective analysis in a single Chinese hospital and literature review

BACKGROUND

We aimed to investigate the clinical characteristics and islet β-cell function in patients with Klinefelter syndrome (KS) and hyperglycemia.

METHODS

This is a retrospective study. In total, 22 patients diagnosed with KS were identified from the electronic medical record system, including 9 patients with hyperglycemia (total patients with hyperglycemia, THG-KS group) and 5 hyperglycemic KS patients with oral glucose tolerance test (OGTT) results (HG-KS group). An additional 5 subjects with hyperglycemia and 5 normal glucose tolerance (NGT) subjects matched based on body mass index were included as the HG group and NGT group, respectively. Data from clinical and laboratory examinations were collected. We further performed a literature review of KS and hyperglycemia.

RESULTS

We found that KS patients developed abnormal glucose metabolism earlier in life than those without KS, and the median age was 17 years, ranging from 10 years to 19 years. Six of 17 (35.3%) patients were diagnosed with diabetes mellitus and 3 of 17 (17.6%) patients were diagnosed with prediabetes. Among 10 patients with both fasting blood glucose and insulin results recorded, there were 8 out of 17 (47.1%) KS patients had insulin resistance. The prevalence of hypertension and dyslipidemia was higher in patients with hyperglycemia and KS than in patients with NGT KS. Compared with the HG group, insulin sensitivity levels were lower in HG-KS group, whereas homeostasis model assessment of β-cell function levels (p = 0.047) were significantly, indicating higher insulin secretion levels in the HG-KS group.

CONCLUSIONS

KS patients develop hyperglycemia earlier in life than those without KS and show lower insulin sensitivity and higher insulin secretion. These patients also have a higher prevalence of other metabolic diseases and may have different frequencies of developing KS-related symptoms.

Serum Prokineticin-2 in Prepubertal and Adult Klinefelter Individuals

The prokineticin-2 (PROK2) is a small peptide belonging to the prokineticin family. In humans and rodents this chemokine is primarily involved in the control of central and peripheral reproductive processes. Klinefelter's syndrome (KS) is the first cause of male genetic infertility, due to an extra X chromosome, which may occur with a classical karyotype (47, XXY) or mosaic forms (46, XY/47, XXY). In affected subjects, pubertal maturation usually begins at an adequate chronological age, but when development is almost complete, they display a primary gonadal failure, with early spermatogenesis damage, and later onset of testosterone insufficiency. Thus, the main aim of the present study was to investigate the serum levels of PROK2 in prepubertal and adult KS patients, comparing them with healthy subjects. We showed for the first time the presence of PROK2 in the children serum but with significant changes in KS individuals. Indeed, compared to healthy subjects characterized by PROK2 serum elevation during the growth, KS individuals showed constant serum levels during the sexual maturation phase (higher during the prepubertal phase but lower during the adult age). In conclusion, these data indicate that in KS individuals PROK2 may be considered a biomarker for investigating the SK infertility process.

Erectile Dysfunction and Decreased Libido in Klinefelter Syndrome: A Prevalence Meta-Analysis and Meta-Regression Study

BACKGROUND

Only few studies have assessed sexual dysfunction in men with Klinefelter syndrome (KS).

AIM

To define pooled prevalence estimates and correlates of erectile dysfunction (ED) and decreased libido (DL) in KS.

METHODS

A thorough search of Medline, Embase and Web of Science was performed to identify suitable studies. Quality of the articles was scored using the Assessment Tool for Prevalence Studies. Data were combined using random effect models and the between-studies heterogeneity was assessed by the Cochrane's Q and I². The sources of heterogeneity were investigated by meta-regression and sub-group analyses. Funnel plot, Begg's rank correlation and trim-and-fill test were used to assess publication bias.

MAIN OUTCOME MEASURE

The pooled prevalence of ED and DL in KS as well as 95% confidence intervals (CIs) were estimated from the proportion of cases of sexual dysfunction and the sample size. Variables that could affect the estimates were identified by linear meta-regression models.

RESULTS

Sixteen studies included collectively gave information about ED and DL in 482 and 368 KS men, respectively, resulting in a pooled prevalence of 28% (95% CI: 19%-36%) for ED and 51% (95% CI: 36%-66%) for DL, with a large heterogeneity. The trim-and-fill adjustment for publication bias produced a negligible effect on the pooled estimates. At the meta-regression analyses, a higher prevalence of ED was significantly associated with an older age but not with lower testosterone levels. In series with a mean age >35 years, the ED prevalence estimate increased up to 38% (95% CI: 31%-44%) with no heterogeneity (I²=0.0%, P=0.6). On the contrary, the prevalence of DL increased significantly as testosterone levels decreased, without a significant relationship with age.

CLINICAL IMPLICATIONS

While DL would largely reflect an androgen deficiency, in older men with KS, erectile function should be assessed irrespective of testosterone levels.

STRENGTH & LIMITATIONS

This is the first meta-analysis defining pooled prevalence estimates and correlates of ED and DL in KS. Nevertheless, caution is required when interpreting results, due to the high risk of bias in many studies, as well as the dearth of data about psychosocial and/or psychosexological variables and age at the diagnosis.

CONCLUSIONS

ED and DL represent common clinical complaints in KS. While the prevalence of ED would increase with age, DL gets more common as serum testosterone decreases. Further studies are warranted to elucidate the pathogenetic mechanism(s) underlying the age-dependent increase in the prevalence of ED, apparently unrelated to the androgenic status. A Barbonetti, S D'Andrea, W Vena, et al. Erectile Dysfunction and Decreased Libido in Klinefelter Syndrome: A Prevalence Meta-Analysis and Meta-Regression Study. J Sex Med 2021;18:1054-1064.

Oncologic manifestations of Klinefelter syndrome

Klinefelter syndrome (47,XXY) has a prevalence of approximately 1 in 500 males. It is a condition characterized by an extra X chromosome and is an underdiagnosed clinical entity. Inactivation of genes enables their escape from regulatory mechanisms, which can result in such classic physical manifestations as hypogonadism, gynecomastia, infertility, and various hormonal and physical abnormalities. While the endocrine manifestations of 47,XXY are well-known, the oncologic manifestations have received less attention. An association between cancer and 47,XXY has not as yet been clearly defined, with variability noted in the prevalence of different malignancies in 47,XXY patients. The mechanisms underlying these altered oncologic risks are still under debate. Some of the proposed explanations include hormone imbalance, developmental malfunctions, and failed DNA repair mechanisms. However, the recognition of the oncological associations linked to 47,XXY could be helpful. Screening measures in certain malignancies may enable an earlier diagnosis of 47,XXY and the implementation of more customized care in 47,XXY and the mosaic variants.. The data for this review was compiled from relevant PubMed articles published within the last three decades and organized based on cancer type.

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.

European academy of andrology guidelines on Klinefelter Syndrome Endorsing Organization: European Society of Endocrinology

BACKGROUND

Knowledge about Klinefelter syndrome (KS) has increased substantially since its first description almost 80 years ago. A variety of treatment options concerning the spectrum of symptoms associated with KS exists, also regarding aspects beyond testicular dysfunction. Nevertheless, the diagnostic rate is still low in relation to prevalence and no international guidelines are available for KS.

OBJECTIVE

To create the first European Academy of Andrology (EAA) guidelines on KS.

METHODS

An expert group of academicians appointed by the EAA generated a consensus guideline according to the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) system.

RESULTS

Clinical features are highly variable among patients with KS, although common characteristics are severely attenuated spermatogenesis and Leydig cell impairment, resulting in azoospermia and hypergonadotropic hypogonadism. In addition, various manifestations of neurocognitive and psychosocial phenotypes have been described as well as an increased prevalence of adverse cardiovascular, metabolic and bone-related conditions which might explain the increased morbidity/mortality in KS. Moreover, compared to the general male population, a higher prevalence of dental, coagulation and autoimmune disorders is likely to exist in patients with KS. Both genetic and epigenetic effects due to the supernumerary X chromosome as well as testosterone deficiency contribute to this pathological pattern. The majority of patients with KS is diagnosed during adulthood, but symptoms can already become obvious during infancy, childhood or adolescence. The paediatric and juvenile patients with KS require specific attention regarding their development and fertility.

CONCLUSION

These guidelines provide recommendations and suggestions to care for patients with KS in various developmental stages ranging from childhood and adolescence to adulthood. This advice is based on recent research data and respective evaluations as well as validations performed by a group of experts.

Testicular blood supply is altered in the 41,XXY* Klinefelter syndrome mouse model

Hypergonadotropic hypogonadism is a major feature of Klinefelter syndrome (KS), assumed to be caused by testicular hormone resistance. It was previously shown that intratesticular testosterone levels in vivo and Leydig cell function in vitro seem to be normal indicating other functional constraints. We hypothesized that impaired testicular vascularization/blood flow could be a co-factor to the observed hypergonadotropic hypogonadism. We evaluated the testicular vascular system by measuring blood vessel sizes during postnatal development and testis blood flow in adult 41,XX^Y* mice. Proportional distribution and size of blood vessels were analyzed during testicular development (1, 3, 5, 7, 10, 21 dpp, 15 wpp). While ratios of the vessel/testis area were different at 15 wpp only, a lower number of smaller and mid-sized blood vessels were detected in adult KS mice. For testicular blood flow determination we applied contrast enhanced ultrasound. Floating and reperfusion time for testicular blood flow was increased in 41,XX^Y* mice (floating: XY* 28.8 ± 1.69 s vs XX^Y* 44.6 ± 5.6 s, p = 0.0192; reperfusion XY* 19.7 ± 2.8 s vs XX^Y*: 29.9 ± 6.2 s, p = 0.0134), indicating a diminished blood supply. Our data strengthen the concept that an impaired vascularization either in conjunction or as a result of altered KS testicular architecture contributes to hormone resistance.

[Evaluation of body composition, resting metabolic rate and frequency of metabolic disorders in adolescents with Klinefelter syndrome]

BACKGROUND

Kleinfelter syndrome (KS) is a common genetic disease characterized by hypergonadotropic hypogonadism. The high risk of developing of metabolic disorders in patients with KS is be explained by the presence of androgen deficiency, which leads to a decrease in the amount of lean soft mass and an increase of the adipose tissue content. The basal metabolic rate (BMR) is determined by the amount of lean soft mass, and its reduction can contribute to weight gain and the progression of metabolic disorders in KS.

AIM

Body composition, assessment of basal metabolism and metabolic profile in adolescents with KS.

MATERIALS AND METHODS

The study included 28 adolescents with KS, comparable in age and stage of sexual maturation. All patients were divided into two groups depending on the presence of clinical laboratory signs of hypogonadism. Patients passed through the evaluation of metabolic profile, bioelectrical impedance analysis for the body composition and chamber-based indirect calorimetry for the evaluation of BMR.

RESULTS

Normal indicants of body composition were determined in 20 (71.4%) adolescents, excess of adipose mass &ndash; in 6 (21.4%) patients, and deficit of adipose mass &ndash; in 7.2% of cases. Among 6 patients with excess of adipose mass, three were obese or overweight, while the rest had normal SDS body mass index (BMI). 64.3% of adolescents showed normal indicants of energy exchange at rest, 6 (21.4%) &ndash; a decrease of BMR, 4 (14.3%) - an increase of BMR. A comparative analysis of patient groups did not reveal statistically significant differences in BMR adjusted to a lean soft mass (OO/TM) (p=0.36). Insulin resistance was detected in 11 patients (39.3%), and the incidence of dyslipidemia was 3.6%. The groups did not significantly differ in terms of glycemia levels in the fasted state and lipid profile indicants.

CONCLUSION

Most adolescents with KS have normal indicants of body composition and basal metabolism, as well as a low frequency of metabolic disorders, regardless of the level of total testosterone in blood. In some patients with normal SDS BMI, excess of adipose mass is detected. The lack of correlation between the level of testosterone and the intensity of BMR may indicate a slight effect of androgen deficiency on energy exchange at rest in adolescents with KS.

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.

Androgens During Infancy, Childhood, and Adolescence: Physiology and Use in Clinical Practice

We provide an in-depth review of the role of androgens in male maturation and development, from the fetal stage through adolescence into emerging adulthood, and discuss the treatment of disorders of androgen production throughout these time periods. Testosterone, the primary androgen produced by males, has both anabolic and androgenic effects. Androgen exposure induces virilization and anabolic body composition changes during fetal development, influences growth and virilization during infancy, and stimulates development of secondary sexual characteristics, growth acceleration, bone mass accrual, and alterations of body composition during puberty. Disorders of androgen production may be subdivided into hypo- or hypergonadotropic hypogonadism. Hypogonadotropic hypogonadism may be either congenital or acquired (resulting from cranial radiation, trauma, or less common causes). Hypergonadotropic hypogonadism occurs in males with Klinefelter syndrome and may occur in response to pelvic radiation, certain chemotherapeutic agents, and less common causes. These disorders all require testosterone replacement therapy during pubertal maturation and many require lifelong replacement. Androgen (or gonadotropin) therapy is clearly beneficial in those with persistent hypogonadism and self-limited delayed puberty and is now widely used in transgender male adolescents. With more widespread use and newer formulations approved for adults, data from long-term randomized placebo-controlled trials are needed to enable pediatricians to identify the optimal age of initiation, route of administration, and dosing frequency to address the unique needs of their patients.

Morbidity in Klinefelter syndrome and the effect of testosterone treatment

Klinefelter syndrome (KS; 47,XXY) is the most common sex chromosome abnormality in males (150 per 100,000 males). The condition leads to hypergonadotropic hypogonadism and ever since the condition was described approximately 80 years ago, testosterone treatment has been the cornerstone in care for individuals with KS. However, KS is associated with an array of health-related and socioeconomic challenges and it is becoming progressively clear that proper care for boys and men with KS reaches far beyond simply supplementing with testosterone. There are no widely implemented guidelines for KS care, and studies investigating crucial aspects of testosterone treatment in individuals with KS, including both beneficial and potentially adverse effects, have only begun to emerge during the last decades. For this descriptive review, we present an overview of literature describing health-related outcomes of testosterone treatment in KS and outline the clinical applications of testosterone treatment in KS. Collectively, beneficial effects of testosterone treatment on overall health in KS are described with few apparent adverse effects. However, larger randomized studies in adult and pediatric patients are warranted to elucidate key aspects of treatment. We stress the implementation of centralized multidisciplinary clinics and the need for a dedicated international guideline to ensure optimal care of boys and men with KS.

Testicular function in boys with 47,XYY and relationship to phenotype

An additional Y chromosome occurs in ~1 in 1,000 males, resulting in the karyotype 47,XYY. The phenotype includes tall stature, hypotonia, neuropsychiatric comorbidities, and an increased risk of infertility in adulthood. Little is known about testicular function in childhood and adolescence in 47,XYY. This cross-sectional study aimed to assess testicular function serum biomarkers, including total testosterone, inhibin B, and anti-mullerian hormone (AMH), in 82 boys with XYY (11.3 ± 3.8 years) compared with 66 male controls (11.6 ± 3.8 years). The association of testicular hormones with physical features, neuropsychological phenotype, and magnetoencephalography (MEG) was assessed with multiple linear regression models. Results indicate males with XYY have significantly lower inhibin B (median 84 pg/ml vs. 109 pg/ml, p = .004) and higher AMH (median 41 ng/ml vs. 29 ng/ml, p = .011); however, testosterone, testicular volume, and stretched penile length were not different from controls. In the exploratory analysis of relationships between hormone concentrations and phenotypic assessments, higher inhibin B concentrations were positively correlated with lower BMI and better cognitive, academic, and behavioral outcomes in the XYY group. Testosterone concentrations were positively associated with better behavioral outcomes in boys with XYY. Higher testosterone and inhibin B concentrations were also associated with shorter auditory latencies measured using magnetoencephalography (MEG) in XYY. With a few exceptions, testicular hormones were not associated with phenotypic outcomes in controls. In conclusion, there is evidence of subtle impaired testicular function in boys with XYY and a newly described relationship between measures of testicular function and some aspects of the XYY phenotype.

Testosterone Therapy in Adolescent Boys: The Need for a Structured Approach

BACKGROUND

In adolescents, testosterone may have several effects including promotion of secondary sexual characteristics and pubertal growth, attainment of optimal muscle mass and peak bone mass, optimization of the metabolic profile, and psychosocial maturation and well-being.

SUMMARY

Testosterone therapy is a cornerstone of the management of hypogonadism in boys. Since the initial report of the chemical synthesis of testosterone, several formulations have continued to develop, and although many of these have been used in boys, none of them have been studied in detail in this age group. Given the wide ranging effects of testosterone, the level of evidence for their effects in boys and the heterogeneity of conditions that lead to early-onset hypogonadism, a standardized protocol for monitoring testosterone replacement in this age group is needed. Key Messages: In this review, we focus on the perceived benefits of androgen replacement in boys affected by pubertal delay and highlight the need to improve the health monitoring of boys who receive androgen replacement therapy, proposing different approaches based on the underlying pathophysiology.

Metabolic and cardiovascular risk factors in Klinefelter syndrome

Klinefelter syndrome (KS), which normally presents with a 47,XXY karyotype, is the most common sex chromosome disorder in males. It is also the most common genetic cause of male infertility. KS subjects are typically tall, with small and firm testes, gynecomastia, broad hips, and sparse body hair, although a less evident presentation is also possible. KS is also characterized by a high prevalence of hypogonadism, metabolic syndrome (MetS) and cardiovascular disease. The aim of this article is to systematically review metabolic and the cardiovascular risk factors in KS patients. Hypogonadism has an important role in the pathogenesis of the changes in body composition (particularly visceral obesity) and hence of insulin resistance and MetS, but the association between KS and MetS may go beyond hypogonadism alone. From childhood, KS patients may show an increase in visceral fat with a reduction in lean body mass and an increase in glucose and impaired fat metabolism. Their increased incidence of congenital anomalies, epicardial adipose tissue, and thromboembolic disease suggests they have a higher risk of cardiovascular disease. There is conflicting evidence on the effects of testosterone therapy on body composition and metabolism.

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.

Klinefelter Syndrome and Diabetes

PURPOSE OF REVIEW

Klinefelter syndrome (KS) is associated with increased insulin resistance and high rates of type 2 diabetes (T2DM). Our aim was to review what is known about the prevalence of diabetes in men with KS, potential mechanisms underlying the observed metabolic phenotype, and the data that are available to guide treatment decisions.

RECENT FINDINGS

The increased prevalence of T2DM seen in men with KS appears to be the result of multiple mechanisms including increased truncal adiposity and socioeconomic disadvantages, but it is likely not a direct consequence of hypogonadism alone. No randomized trials have been conducted to evaluate the impact of testosterone replacement therapy on T2DM in men with KS, but observational data suggest that testosterone replacement is not associated with lower rates of diabetes or improved glycemic control. Metabolic derangements are common in KS, but treatment strategies specific to this population are lacking. Early lifestyle and dietary interventions are likely important. Additional research is needed to dissect the complex interaction between genotype and metabolic phenotype. Collaboration between academic centers caring for men with KS is needed to facilitate the development of evidence-based clinical practice guidelines, which would inform optimal screening and treatment strategies for this patient population.

Endocrine aspects of Klinefelter syndrome

PURPOSE OF REVIEW

Klinefelter syndrome is the most common sex chromosome abnormality in men. Hypogonadism and testicular degeneration are almost universal. Truncal adiposity, metabolic syndrome and low bone mass occur frequently. This review summarizes the most recent advances in the pathogenesis and management of the endocrine abnormalities in Klinefelter syndrome. It is expected that optimal endocrine management will improve outcomes and quality of life in Klinefelter syndrome.

RECENT FINDINGS

In Klinefelter syndrome, testosterone replacement is routinely prescribed despite lack of evidence on the optimal dose and time for initiation of therapy. Cross-sectional studies have linked hypogonadism to the development of metabolic abnormalities and low bone mass. Testosterone therapy, however, is not consistently associated with improved metabolic and bone outcomes. Increased truncal adiposity and high rates of metabolic syndrome are present in prepubertal children. A randomized trial of oxandrolone in prepubertal boys showed improvement in visual-motor function, socialization and cardiometabolic health. Testicular sperm extraction (TESE) has success rates similar to other causes of nonobstructive azoospermia when performed between 16 and 35 years of age.

SUMMARY

Endocrine care in Klinefelter syndrome should start in childhood and include evaluation of metabolic risk factors and bone health. Further research to guide evidence-based endocrine care is very much needed.

Evaluation of testicular function in prepubertal children

INTRODUCTION

The assessment of testicular function is not currently performed in childhood. The aim of this review was to address the usefulness of serum Anti-Müllerian Hormone (AMH), inhibin B, and testicular volume (TV) evaluation in children.

REVIEW

Serum AMH and inhibin B levels reflect Sertoli cells (SCs) health and number, SCs maturation degree and their exposure to FSH and to intra-tubular testosterone (T). These hormones might be helpful in discriminating between congenital central hypogonadism (cHH) and constitutional delay in growth and puberty (CDGP) and in case of clinical suspicious of precocious puberty. Furthermore, low AMH and/or inhibin B levels have been observed in children with primary testicular disorders, suggesting the existence of SC dysfunction. TV also provides useful information on testicular health. Recently, a medical calculator, requiring testis length and the stage of genital development, has been developed to easily derive TV.

CONCLUSIONS

The evidence supports the usefulness of AMH, inhibin B and TV evaluation for the early diagnosis of puberty disorders and primary testicular damage. We suggest the measurement of TV by using the medical calculator in all children and to reserve AMH and inhibin B measurements to those cases of no testicular growth, clinical suspicious of puberty disorders or in children at risk for spermatogenesis damage. This work-up might allow the early detection of testicular tubular damage which, in turn, may be useful to prevent the oncoming male infertility in adulthood.

Oxandrolone Treatment Results in an Increased Risk of Gonadarche in Prepubertal Boys With Klinefelter Syndrome

CONTEXT

Klinefelter syndrome (KS) is a common genetic condition in which males have an extra X chromosome. KS is associated with testosterone deficiency, neurodevelopmental delays, and cardiometabolic disorders. There has been recent interest in prepubertal androgen treatment; however, the effects on puberty and gonadal function are unknown.

OBJECTIVE

To compare onset of puberty and testicular function in prepubertal boys treated with 2 years of oxandrolone (Ox) vs placebo (Pl).

DESIGN

Double-blind, randomized, controlled trial.

SETTING

Single tertiary care referral center.

PARTICIPANTS

Eighty prepubertal boys with KS; mean age: 8.0 ± 2.2 years (range: 4 to 12).

INTERVENTIONS

Ox 0.05 mg/kg vs identical-appearing Pl capsule given for 2 years.

OUTCOME MEASURES

Onset of gonadarche (testicular volume ≥4 mL) and onset of pubarche (Tanner 2 pubic hair); change in testicular hormone concentrations.

RESULTS

Ox-treated group had 20.5 times higher odds of reaching gonadarche (OR 95% CI: 6.5, 77.8) and 28.1 times higher odds of reaching pubarche (OR 95% CI: 8.8, 110.4) during the 2-year study period after adjusting for baseline age. Gonadarche and pubarche both occurred at a younger age in the Ox group (gonadarche: 9.8 ± 1.5 vs 12.1 ± 1.0 years, P < 0.001; pubarche: 10.2 ± 1.1 vs 11.6 ± 1.3 years, P = 0.02). Serum concentrations of testicular hormones and gonadotropins were not different between groups.

CONCLUSIONS

Two years of Ox treatment in prepubertal boys with KS results in an increased risk of early gonadarche, on average 2 years earlier than in Pl-treated boys. Ox did not affect serum concentrations of testicular hormones.

Klinefelter Syndrome: Integrating Genetics, Neuropsychology, and Endocrinology

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.

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.

Androgen Treatment Effects on Motor Function, Cognition, and Behavior in Boys with Klinefelter Syndrome

OBJECTIVES

To examine the effects of early low-dose androgen on motor, cognitive, and behavioral function in prepubertal boys with Klinefelter syndrome (47,XXY).

STUDY DESIGN

Double-blind trial of 84 boys, ages 4-12 years, randomized to oxandrolone (Ox; 0.06?mg/kg daily; n?=?43) or placebo (Pl; n?=?41) for 24 months. Standardized assessments were performed at baseline and every 12 months for 24 months evaluating motor, cognitive, and behavioral function.

RESULTS

The 24-month outcomes were better in the Ox vs. Pl group on 1 of 5 primary endpoints (motor function/strength): Bruininks Visual-Motor scale (P?=?.005), without significant differences between the 2 groups for the other 4 components. Secondary analyses suggested improvement in the Ox vs. Pl group in the anxiety/depression (P?=?.03) and social problems (P?=?.01) scales on the Child Behavior Checklist, anxiety (P?=?.04) on the Piers Harris Self Concept Scale, and interpersonal problems (P?=?.02) on the Children's Depression Inventory, without significant differences in hyperactive or aggressive behaviors.

CONCLUSIONS

This double-blind, randomized trial demonstrates that 24 months of childhood low-dose androgen treatment in boys with Klinefelter syndrome benefited 1 of 5 primary endpoints (visual-motor function). Secondary analyses demonstrated positive effects of androgen on aspects of psychosocial function (anxiety, depression, social problems), without significant effects on cognitive function, or hyperactive or aggressive behaviors.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00348946.

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.