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Précis:We studied the effect of 2 years of low-dose androgen therapy (oxandrolone) in children with Klinefelter syndrome and found improvement of body composition and fasting triglycerides.AbstractContext: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.

Abstract 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 still poses diagnostic challenges and many cases remain undiagnosed. Here we review new aspects of the syndrome and integrate genetics, neurocognition, and endocrinology.

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. To compare onset of puberty and testicular function in prepubertal boys treated with 2 years of oxandrolone (Ox) vs placebo (Pl). Double-blind, randomized, controlled trial. Single tertiary care referral center. Eighty prepubertal boys with KS; mean age: 8.0 ± 2.2 years (range: 4 to 12). Ox 0.05 mg/kg vs identical-appearing Pl capsule given for 2 years. Onset of gonadarche (testicular volume ≥4 mL) and onset of pubarche (Tanner 2 pubic hair); change in testicular hormone concentrations. 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. 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.

Differences between female and male immunity may contribute to variations in response to infections and predisposition to autoimmunity. We previously reported that neutrophils from reproductive-age males are more immature and less activated than their female counterparts. To further characterize the mechanisms that drive differential neutrophil phenotypes, we performed RNA sequencing on circulating neutrophils from healthy adult females and males. Female neutrophils displayed significant up-regulation of type I IFN (IFN)-stimulated genes (ISGs). Single-cell RNA-sequencing analysis indicated that these differences are neutrophil specific, driven by a distinct neutrophil subset and related to maturation status. Neutrophil hyperresponsiveness to type I IFNs promoted enhanced responses to Toll-like receptor agonists. Neutrophils from young adult males had significantly increased mitochondrial metabolism compared to those from females and this was modulated by estradiol. Assessment of ISGs and neutrophil maturation genes in Klinefelter syndrome (47, XXY) males and in prepubescent children supported that differences in neutrophil phenotype between adult male and female neutrophils are hormonally driven and not explained by X chromosome gene dosage. Our results indicate that there are distinct sex differences in neutrophil biology related to responses to type I IFNs, immunometabolism, and maturation status that may have prominent functional and pathogenic implications.

Abstract Objective High-grade aneuploidies of X and Y sex chromosomes (HGAs) are exceedingly rare and complex conditions. We aimed to investigate the effect of supernumerary X chromosomes (extra-Xs) on the clinical, hormonal, metabolic, and echocardiographic features of patients with HGAs. Design and Methods In a cross-sectional study, we compared 23 subjects with HGAs and 46 age-matched subjects with 47,XXY Klinefelter syndrome (KS), according to the number of extra-Xs: two (47,XXY and 48,XXYY), three (48,XXXY and 49,XXXYY), or four supernumerary Xs (49,XXXXY). A second cohort consisting of 46 pubertal stage-matched KS subjects was employed for validation. Clinical, hormonal, metabolic and ultrasonographic parameters were collected and analyzed. Results The increase in the number of extra-Xs was associated with a progressive adverse effect on height, pubertal development, testicular volume and function, adrenal steroidogenesis, and thyroid function. A progressive linear increase in ACTH and a decrease in cortisol/ACTH ratios were found. Weight and body mass index, Sertoli cell function, lipid profile, and glucose tolerance post-oral glucose tolerance test were all worse in the HGA cohort compared to KS. Cardiac evaluation revealed a linear association with reduced left and right end-diastolic diameters and reduced ejection fraction. Conclusion The increase in the number of extra-Xs is associated with a “dose-dependent” progressive impairment in steroid producing glands, thyroid function, cardiac structure, and performance.

Although Klinefelter syndrome (KS) is common, it is rarely recognised in childhood, sometimes being identified with speech or developmental delay or incidental antenatal diagnosis. The only regular feature is testicular dysfunction. Postnatal gonadotropin surge (mini-puberty) may be lower, but treatment with testosterone needs prospective studies. The onset of puberty is at the normal age and biochemical hypogonadism does not typically occur until late puberty. Testosterone supplementation can be considered then or earlier for clinical hypogonadism. The size at birth is normal, but growth acceleration is more rapid in early and mid-childhood, with adult height greater than mid-parental height. Extreme tall stature is unusual. The incidence of adolescent gynaecomastia (35.6%) is not increased compared with typically developing boys and can be reduced or resolved by testosterone supplementation, potentially preventing the need for surgery. Around two-thirds require speech and language therapy or developmental support and early institution of therapy is important. Provision of psychological support may be helpful in ameliorating these experiences and provide opportunities to develop strategies to recognise, process and express feelings and thoughts. Boys with KS are at increased risk of impairment in social cognition and less accurate perceptions of social emotional cues. The concept of likely fertility problems needs introduction alongside regular reviews of puberty and sexual function in adolescents. Although there is now greater success in harvesting sperm through techniques such as testicular sperm extraction, it is more successful in later than in early adolescence. In vitro maturation of germ cells is still experimental.

Purpose The role of osteocalcin (OCN) in pubertal development, male hypogonadism, and the effect of testosterone (Te) replacement therapy (TRT) remains unclear. We aimed to investigate the total OCN (tOCN) concentrations in male patients with Klinefelter syndrome (KS), a model of adult hypergonadotropic hypogonadism. Methods This retrospective longitudinal study investigated 254 male patients with KS (47,XXY) between 2007 and 2021 at an academic referral center, categorized as (1) prepubertal, (2) pubertal, and (3) adults. All prepubertal patients were Te-naïve. Adult patients were subcategorized as (1) eugonadal, (2) hypogonadal, and (3) receiving TRT. We also analyzed 18 adult patients with available tOCN levels before and 3 months after TRT commencement. Results The tOCN levels varied throughout the lifespan according to pubertal status, were highest in eugonadal and significantly lower in TRT subjects, correlated with both LH ( p  = 0.017) and FSH levels ( p  = 0.004) in adults, and significantly declined after 3 months of TRT ( p  = 0.006) in the adult KS cohort. HPG-axis hormones levels demonstrated no correlation in prepubertal boys. Adjustment for age and body mass index confirmed previous results and revealed significant inverse correlations with total Te ( p  = 0.004), calculated free Te ( p  = 0.016), the Te/LH ( p  = 0.010), and calculated free Te/LH ratios ( p  = 0.031). Conclusion In KS, a model of male hypergonadotropic hypogonadism, tOCN levels were not associated with gonadal function during normal prepuberty and pubertal development but were associated with worse testicular function and a higher degree of HPG stimulation in adults. TRT acutely reduced tOCN levels in adults.

Background Klinefelter syndrome (KS) frequently causes skeletal fragility characterized by profound alterations in bone microstructure with increased risk of fractures. Increased body fat mass associated with decreased body lean mass are frequent features of KS with possible detrimental effects on skeletal health. In this cross-sectional study, we evaluated the associations between body composition parameters, vertebral fractures (VFs) and trabecular bone score (TBS) in adult subjects with KS. Methods Seventy-one adult males (median age 41 years, range 18–64) with 47, XXY KS were consecutively enrolled by two Endocrinology and Andrology Units (IRCCS Humanitas Research Hospital in Milan and ASST Spedali Civili in Brescia). Dual-energy X-ray absorptiometry (DXA) was performed to assess bone mineral density (BMD) at lumbar spine, femoral neck and total hip, TBS and body composition. Prevalence of VFs was assessed by quantitative morphometry on lateral spine X-rays. Results VFs were detected in 14 patients (19.7%), without significant association with low BMD ( p  = 0.912). In univariate logistic regression analysis, VFs were significantly associated with truncal/leg fat ratio (OR 2.32 per tertile; 95% CI 1.05–5.15; p  = 0.038), whereas impaired TBS (detected in 23.4% of subjects) was associated with older age at study entry ( p  = 0.001) and at diagnosis of disease ( p  = 0.015), body mass index (BMI; p  = 0.001), waist circumference ( p  = 0.007), fat mass index (FMI; p  < 0.001), FMI/lean mass index (LMI) ratio ( p  = 0.001). Prevalence of VFs was not significantly different between subjects with impaired TBS as compared to those with normal TBS (26.7 vs. 18.4%; p  = 0.485). Skeletal end-points were not significantly associated with duration of testosterone replacement therapy and serum testosterone and 25hydroxyvitamin D values. Conclusion Body composition might influence bone quality and risk of VFs in subjects with KS.

Context Klinefelter syndrome (KS) is associated with hypergonadotropic hypogonadism, which contributes to characteristic phenotypical manifestations including metabolic alterations. Extensive research has demonstrated important associations between androgens and liver function. Objectives Investigation of the association between metabolic parameters, sex hormones and liver function in males with KS, both treated (T-KS) and untreated (U-KS) and healthy control males. Methods A total of 65 KS males were recruited, of which 32 received testosterone replacement therapy (TRT). Also, 69 healthy controls were recruited. We used alanine aminotransferase (ALAT), alkaline phosphatase and PP (prothrombin-proconvertin time ratio) as the main liver markers. Multivariable regression was performed within the three groups. All statistics were calculated using STATA. Principal component analysis was utilized to demonstrate the interconnected patterns among all measured biomarkers, and to elucidate how the different groups were linked to these patterns. Results Higher levels of main liver markers were observed in U-KS compared to controls, with no significant differences between U-KS and T-KS. T-KS had lower abdominal fat, total cholesterol, and LDL cholesterol than U-KS. Using multivariable models, variation in ALAT in U-KS was explained by HOMA2%S; in T-KS by BMI and SHBG; and in controls by hip circumference and estradiol. We found no multivariable models explaining variation in PP in U-KS; in T-KS, PP was explained by BMI and LDL cholesterol, and in controls by total cholesterol. Using principal component analysis U-KS was positively associated to D1 (an obese profile, which also included ALAT) and controls negatively associated with D1 (non-obese profile). Conclusion KS males have mild liver dysfunction reflected by a significant increase in the main liver markers and decrease in albumin. The presented data underscore a primary role of metabolic conditions including obesity, insulin resistance and unfavourable lipid profile, in the elevated liver function markers seen in males with KS. Whether TRT can improve liver function in KS warrants further studies. Our findings, highlight that an evaluation of the liver function should be part of the clinical care in males with KS.

The aim was to define the true incidence of gynaecomastia in adolescent boys with Klinefelter syndrome (KS) and to observe testosterone treatment effects on its duration by examination of the prospectively collected data from a specialist referral clinic for boys with KS, with comparison being made with KS boys identified by a historical newborn chromosome screening programme, together with chromosomally normal controls. Fifty-nine boys over age 13 years were referred to a specialist KS clinic; 21 developed gynaecomastia. The comparator was 14 KS boys identified at birth and 94 chromosomally normal control boys. Testosterone was routinely started at the onset of puberty if gynaecomastia, a manifestation of clinical hypogonadism, was present. Oral or transdermal testosterone was administered in the morning, in a reverse physiological rhythm, and doses were increased according to standard pubertal regimens. The incidence of gynaecomastia was not increased in both the KS cohorts compared with controls. The incidence and age of onset of gynaecomastia was 35.6%, at 12.3 (1.8) years in the KS clinic group; 36.0%, at 13.7 (0.6) years in the newborn survey group; and 34.0%, at 13.6 (0.8) years in the controls. Full resolution of the gynaecomastia occurred in the 12/14 KS clinic boys on testosterone treatment who had completed puberty and as long as adherence was maintained.Conclusion: The incidence of gynaecomastia in KS boys (overall 35.6%) is not increased over typically developing boys. Commencing testosterone when gynaecomastia develops with physiological dose escalation and full adherence can result in the resolution of the gynaecomastia. What is Known:• Gynaecomastia is a common feature in Klinefelter syndrome men.• Hypogonadism occurs from mid-puberty onwards with the absence of the usual rise in testosterone levels.What is New:• The incidence of pubertal gynaecomastia in Klinefelter syndrome is not different from typically developing boys.• Early and prompt starting of testosterone gel treatment and increasing the dose physiologically may help to resolve the gynaecomastia without the need for surgery.