Klinefelter syndrome is a frequent cause of hypogonadism, but despite hundreds of publications on different aspects of Klinefelter syndrome, only a few studies dealt with sexual dysfunction. In particular, testosterone is critical for various aspects of sexual response, but its role on sexuality in Klinefelter syndrome patients is debatable and no studies have evaluated the efficacy of testosterone treatment on sexual dysfunction in these subjects. Furthermore, the impact of psychological and relational aspects on sexual function of Klinefelter syndrome subjects is poorly defined. In this study, we aimed to determine the presence and type of sexual dysfunctions in Klinefelter syndrome subjects; to correlate them with testosterone levels and psychosexological and relational domains; and to evaluate the effects of testosterone therapy. We studied 62 non-mosaic naïve Klinefelter syndrome patients and 60 age-matched controls by means of medical history, psychosexological history, 15-item International Index of Erectile Function questionnaire, endocrine assessment, and dynamic penile color Doppler ultrasound. Twenty-five hypogonadal Klinefelter syndrome patients were studied after 6 months of testosterone replacement therapy. Klinefelter syndrome subjects have reduced 15-item International Index of Erectile Function scores regarding sexual desire, intercourse satisfaction, and overall satisfaction with respect to controls, and these aspects were significantly associated with testosterone levels. Klinefelter syndrome subjects had also higher prevalence of erectile dysfunction, but no relation with testosterone levels was evident. A high prevalence of a range of psychological disturbances was present in Klinefelter syndrome subjects with erectile dysfunction with respect to those without erectile dysfunction. No statistical difference in the prevalence of premature and delayed ejaculation was observed between Klinefelter syndrome and control subjects. Testosterone replacement therapy improved sexual desire, intercourse satisfaction, and overall satisfaction scores, but had no effect on erectile function. Penile color Doppler ultrasound was normal in all subjects. This study shows that sexual dysfunction in Klinefelter syndrome is multifactorial and related only in part to hypogonadism and largely to psychological disturbances. Evaluation and therapy of sexual dysfunction should include a combined andrological and psychosexological approach.
Mazzilli R et al., 2026·Journal of endocrinological investigation
Male factor could contribute, alone or in combination with female factor, to the inability to conceive in a couple in more than half of cases. The effect of male factor infertility (MFI) on embryological assisted reproductive technology (ART) outcomes remains an ongoing discussion.
to evaluate the impact of MFI on embryo aneuploidy rates, to better understand the role and possible indication for Preimplantation genetic testing for aneuploidies (PGT-A), considering the role of sperm characteristics, paternal age, sperm DNA fragmentation and sperm aneuploidies.
this narrative review included all available articles, published up to January 2026.
Available evidence, often based on heterogeneous and old-fashioned methodologies, suggests that MFI may impair embryonic development, particularly in terms of fertilization rate and blastulation rate, more than embryo euploidy; however, a comprehensive evaluation of MFI should be integrated into clinical practice in the context of couple infertility, to also optimize the efficiency and outcomes of ART. Promising results emerged from sperm DNA fragmentation as a tool to predict embryo euploidy, but further investigations involving larger sample sizes and improved standardization are required.
Grande G et al., 2026·The Journal of clinical endocrinology and metabolism·Free to read
Male factor infertility (MFI) is frequently labelled idiopathic when evaluation relies primarily on semen analysis, potentially overlooking endocrine and pathophysiological mechanisms relevant for targeted management.
To phenotypically define MFI and develop a pathophysiology-based classification aimed at reducing idiopathic infertility following comprehensive evaluation.
Prospective monocentric cohort study conducted at a tertiary referral academic centre.
Eight hundred male partners of infertile couples evaluated between October 2024 and January 2026 after exclusion of isolated female factor infertility.
Prevalence of MFI categories, hormonal patterns across phenotypes, and proportion of idiopathic infertility after comprehensive work-up.
All patients underwent standardized clinical evaluation, hormonal assessment (total testosterone, FSH, LH), testicular ultrasound, and complete semen analysis. Microbiological testing, transrectal ultrasound, and genetic analyses were performed according to guidelines.
Primary spermatogenic failure was the most prevalent category (56.0%), followed by infection/inflammation (22.4%) and hypogonadotropic hypogonadism (8.5%). Idiopathic infertility was identified in only 5.3% of cases. Distinct endocrine profiles were observed, with high-FSH spermatogenic failure representing the dominant phenotype.
Comprehensive phenotyping markedly reduces the proportion of patients classified as having idiopathic infertility and identifies clinically relevant subgroups. This prospective study provides validation of a pathophysiology-based classification and supports a shift toward endocrine-integrated diagnostic strategies in male infertility, with potential implications for targeted management.
Besides gonadal involvement (hypogonadism, male factor infertility, and testicular hypotrophy), patients with Klinefelter syndrome (KS) may suffer from several extra-gonadic complications, including neoplastic events.
The aim of this review is to summarize all major clinical evidence dealing with the association between KS and neoplastic diseases and provide practical suggestions for the management of patients with KS regarding neoplastic risk.
This narrative review was conducted through a comprehensive search of the PubMed database, using combinations of the following keywords: "Klinefelter syndrome," "cancer," "neoplasm," "breast cancer," "germ cell tumor," "lymphoma," and "testosterone replacement therapy".
KS is associated with a higher risk of breast cancer and mediastinal germ cell tumors and an apparent higher risk of hematological malignancies, in particular non-Hodgkin lymphoma and leukemia. Evidence on testicular cancer is limited, with no clear increase in risk attributable to KS, while prostate cancer has a lower risk and lower mortality rate.
Given the complexity of the syndrome and the limited available evidence, regular clinical follow-up with targeted investigations when clinically indicated may facilitate early diagnosis and management of associated comorbidities.
Male Endocrine and Genetic Factors · Genetic Causes of Male Infertility
Genetic variability within the follicle-stimulating hormone (FSH)-related genes might contribute to phenotypic heterogeneity in patients with Klinefelter syndrome (KS), yet its clinical impact on sperm retrieval remains unclear.
To investigate the association between FSHB c.211 G > T and FSHR polymorphisms (c.2039 A > G and c.29 G > A) and hormonal parameters, as well as their potential role in predicting sperm retrieval rate (SRR) in patients with KS undergoing testicular sperm extraction (TESE).
A retrospective cohort of patients with KS was analyzed. Only subjects not receiving testosterone replacement therapy were included (n = 417). Hormonal, anthropometric, and clinical variables were compared across genotypes using nonparametric tests. Additive genetic models were applied to evaluate allele-dose effects. Multivariable logistic regression was performed to identify independent predictors of SRR. Predictive performance of clinical and combined clinical-genetic models was assessed using ROC curve analysis.
FSHB and FSHR genes polymorphisms were associated with variations in serum FSH concentrations, confirming a modulatory role of the FSH-related genes. In additive modeling, the FSHR c.29 G > A polymorphism emerged as an independent predictor of SRR (adjusted OR: 0.29; 95% CI, 0.09-0.97), whereas FSHB c.211 G > T showed a nonsignificant trend. The inclusion of genetic variants modestly improved predictive accuracy compared with clinical variables alone, as demonstrated by ROC analysis.
Genetic variants within the genes involved in FSH action might contribute incremental information for the prediction of sperm retrieval in patients with KS. While the overall predictive gain remains moderate, additive genetic modeling highlights a potential allele-dose effect of FSHR c.29 G > A on reproductive outcome, supporting a role for integrated clinical-genetic assessment in this population, although external validation remains required.
Barbonetti A et al., 2021·The journal of sexual medicine
Only few studies have assessed sexual dysfunction in men with Klinefelter syndrome (KS).
To define pooled prevalence estimates and correlates of erectile dysfunction (ED) and decreased libido (DL) in KS.
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.
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.
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.
While DL would largely reflect an androgen deficiency, in older men with KS, erectile function should be assessed irrespective of testosterone levels.
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.
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.
Male Endocrine and Genetic Factors · Genetic Causes of Male Infertility
Klinefelter syndrome (KS) is a common genetic disorder characterized by an additional X chromosome in males. A deficient androgen production and a varied observed response of end-organs to testosterone can lead to delayed progression of puberty with reduction in muscle development and facial/body hair, osteoporosis, and gynecomastia. Medical management during puberty focuses on the preservation of fertility and testosterone replacement treatment (TRT) to reduce the current or future consequences of testicular fibrosis. However, more research is needed to establish the need and conditions for TRT in adolescence, as well as the opportunity and timing for sperm recovery in adolescents and young boys with KS. Furthermore, screening for associated diseases such as metabolic syndrome, osteoporosis, and malignancies should be guaranteed during this lifetime. Preventive care should be provided by diagnosis, ideally through a multidisciplinary approach.
Pizzocaro A et al., 2020·Journal of endocrinological investigation
Low testosterone (T) in Klinefelter's syndrome (KS) can contribute to typical features of the syndrome such as reduced bone mineral density, obesity, metabolic disturbances and increased cardiovascular risk. The aim of the present study is to review and meta-analyze all available information regarding possible differences in metabolic and bone homeostasis profile between T treated (TRT) or untreated KS and age-matched controls.
We conducted a random effect meta-analysis considering all the available data from observational or randomized controlled studies comparing TRT-treated and untreated KS and age-matched controls. Data were derived from an extensive MEDLINE, Embase, and Cochrane search.
Out of 799 retrieved articles, 21 observational and 22 interventional studies were included in the study. Retrieved trials included 1144 KS subjects and 1284 healthy controls. Not-treated KS patients showed worse metabolic profiles (including higher fasting glycemia and HOMA index as well as reduced HDL-cholesterol and higher LDL-cholesterol) and body composition (higher body mass index and waist circumference) and reduced bone mineral density (BMD) when compared to age-matched controls. TRT in hypogonadal KS subjects was able to improve body composition and BMD at spinal levels but it was ineffective in ameliorating lipid and glycemic profile. Accordingly, TRT-treated KS subjects still present worse metabolic parameters when compared to age-matched controls.
TRT outcomes observed in KS regarding BMD, body composition and glyco-metabolic control, are similar to those observed in male with hypogonadism not related to KS. Moreover, body composition and BMD are better in treated than untreated hypogonadal KS. Larger and longer randomized placebo-controlled trials are advisable to better confirm the present data, mainly derived from observational studies.
Guidelines by Clinical Area · Bone and Endocrine Guidelines
Zitzmann M et al., 2025·The aging male : the official journal of the International Society for the Study of the Aging Male·Free to read
This is the inaugural recommendation for the management of the Aging Male with Klinefelter Syndrome (KS), a demographic characterized by primary hypogonadism in the presence of one or more supernumerary X-chromosomes with irregular gene-inactivation, and metabolic dysregulation, contributing a component of functional hypogonadism as aging in these men progresses. The unique constellation of symptoms spanning multiple organ systems and health domains necessitates specialized diagnostic and therapeutic strategies. Neglecting the specific needs of this population can precipitate a considerable decline in quality of life and overall health outcomes. Our recommendations advocate for a multidisciplinary approach involving endocrinologists, urologists, geneticists, mental health professionals, and other specialists, to address the complex interplay of hormonal imbalances, metabolic disorders, cardiovascular risk factors including arrhythmia, bone health concerns, psychological and sexual challenges, ophthalmological problems, and dental issues. By providing a structured framework for comprehensive and individualized care, these recommendations aim to bridge existing healthcare gaps, optimize well-being, and enhance the overall quality of life for aging men with KS.
Mental Health and Psychosocial Care › Psychosocial Support › Counseling and Therapy · Therapeutics › Hormonal Agents › Androgens and DHEA
M Di Grazia, A Di Mambro
PMID 29453817 29453817 DOI 10.1111/andr.12474 10.1111/andr.12474 Ferlin et al. 2018, Ferlin 2018
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