Research Methods · Preclinical Research
Rocca MS, Ferrarini M, Msaki A, Vinanzi C, Ghezzi M, De Rocco Ponce M, Foresta C, Ferlin A
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The androgen receptor (AR) is a nuclear receptor, encoded by the AR gene on the X chromosome. Within the first exon of the AR gene, two short tandem repeats (STR), CAG and GGC, are a source of polymorphism in the population. Therefore, high-throughput methods for screening AR, such as next-generation sequencing (NGS), are sought after; however, data generated by NGS are limited by the availability of bioinformatics tools. Here, we evaluated the accuracy of the bioinformatics tool HipSTR in detecting and quantify CAG repeats within the AR gene.
The AR gene of 228 infertile men was sequenced using NGSgene panel. Data generated were analyzed with HipSTR to detect CAG repeats. The accuracy was compared with the results obtained with Sanger.
We found that HipSTR was more accurate than Sanger in genotyping normal karyotype men (46,XY), however, it was more likely to misidentify homozygote genotypes in men with Klinefelter syndrome (47,XXY).
Our findings show that the bioinformatics tool HipSTR is 100% accurate in detecting and assessing AR CAG repeats in infertile men (46,XY) as well as in men with low-level mosaicism.
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.
Rocca MS et al., 2026 · Journal of translational medicine · Free to read
Standard semen analysis has little prognostic value in distinguishing fertile from infertile men. Furthermore, in men with semen parameters within the reference ranges, it cannot distinguish fertile men from infertile men, i.e. partners of couples with idiopathic infertility. Oxidative stress, mitochondrial dysfunction, sperm telomere shortening, and DNA fragmentation have been proposed as contributors to impaired male fertility. However, these biomarkers have not been evaluated as a whole in subjects with normal semen parameters, partners of fertile and infertile couples. To characterise a multidimensional panel of sperm biomarkers-including sperm telomere length (STL), mitochondrial DNA copy number (mtDNAcn), reactive oxygen species (ROS), lipid peroxidation (LP), sperm chromatin dispersion (SCD), and respiratory control ratio (RCR)-and to identify whether these parameters might discriminate, in men with normal semen parameters, infertile men from fertile controls. A total of 150 men with semen parameters within the normal ranges were enrolled: 47 male partners of couples with idiopathic infertility and 103 fertile controls. STL and mtDNAcn were quantified by qPCR; ROS were assessed using OxiSperm®II with semiquantitative imaging; LP was measured spectrophotometrically in seminal plasma; SCD was used to determine DNA fragmentation; and mitochondrial function was evaluated by oxygen consumption and RCR. Correlations between biomarkers and semen parameters were analysed using Pearson or Spearman coefficients, and intergroup comparisons were adjusted for age. Semen parameters did not differ significantly between male partners of fertile and infertile couples. compared to men of fertile couples, men of infertile couples exhibited significantly shorter STL (0.57 ± 0.59 vs 1.21 ± 1.13, p_adj = 0.001) and higher oxidative stress, with both ROS (8300.9 ± 4214.8 vs 6555.3 ± 3394.3, p_adj = 0.027) and LP (88.33 ± 55.50 vs 40.29 ± 46.98, p_adj < 0.001) markedly elevated. mtDNAcn, SCD, and RCR showed no difference between the groups. Across the entire cohort, STL correlated negatively with ROS and LP and positively with RCR. ROS correlated negatively with total sperm count, motility and RCR, and positively with LP. LP displayed the strongest pattern of associations, correlating negatively with concentration, total count, motility, STL and RCR, and positively with age and volume. Among men with normal semen analysis, partners of couples with idiopathic infertility exhibit a distinct sperm molecular profile characterised by telomere shortening and oxidative imbalance. STL, ROS and LP emerged as age-independent biomarkers associated with infertility status and showed promising discriminatory ability in this cohort, supporting their integration as second-level tests to complement routine semen analysis in cases of normozoospermia.
Graziani A et al., 2026 · Andrology · Free to read
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.
Rocca MS et al., 2023 · The Journal of clinical endocrinology and metabolism
Mutations in the androgen receptor (AR) gene might be associated with infertility mainly because they cause various degrees of androgen insensitivity. The aim of the study was to evaluate the frequency and type of AR variants in a large cohort of infertile males. A total of 8224 males of Italian idiopathic infertile couples were referred to the University Hospital of Padova. The main outcome measures were mutational screening of AR, computational, and functional analyses. We found 131 patients (1.6%) harboring 45 variants in AR gene, of which 18 were novel missense AR variants. Patients with AR gene variants had lower sperm count (P = .048), higher testosterone (T) concentration (P < .0001), and higher androgen sensitivity index (ASI) (luteinizing hormone × T, P < .001) than patients without variants. Statistical analyses found T ≥ 15.38 nmol/L and ASI ≥ 180 IU × nmol/L2 as the threshold values to discriminate with good accuracy patients with AR variants. Patients with oligozoospermia and T ≥ 15.38 nmol/L had a 9-fold increased risk of harboring mutations compared with patients with normal sperm count and T < 15.38 nmol/L (odds ratio 9.29, 95% CI 5.07-17.02). Using computational and functional approaches, we identified 2 novel variants, L595P and L791I, as potentially pathogenic. This is the largest study screening AR gene variants in men of idiopathic infertile couples. We found that the prevalence of variants increased to 3.4% in oligozoospermic subjects with T ≥ 15.38 nmol/L. Conversely, more than 80% of men with AR gene variants had low sperm count and high T levels. Based on our findings, we suggest AR sequencing as a routine genetic test in cases of idiopathic oligozoospermia with T ≥ 15.38 nmol/L.
Graziani A et al., 2026 · Andrology · Free to read
Klinefelter syndrome (KS) is characterized by marked phenotypic heterogeneity that might be influenced by genetic modifiers, including androgen receptor (AR) repeat length (CAGn and GGCn). The clinical relevance of these repeat lengths in patients with KS before testosterone replacement therapy (TRT) remains unclear. To investigate the association between AR repeat length and anthropometric, hormonal, metabolic, and reproductive parameters in a well-characterized cohort of untreated adult patients with KS. In this cross-sectional single-center study, 214 men with classical 47, XXY karyotype were evaluated prior to TRT. Clinical, biochemical, and reproductive parameters were analyzed according to AR CAGn and GGCn repeat length. Nonparametric tests, multivariable linear and logistic regression models, and interaction terms between CAGn and GGCn were tested. Standardized beta coefficients were used to compare the relative contribution of AR repeat length with major clinical determinants. In unadjusted analyses, CAG repeat length was associated with estradiol concentrations, whereas GGC repeat length showed associations with hematocrit, platelet count, and total cholesterol. However, most associations were characterized by small effect sizes and did not persist after multivariable adjustment for possible confounders (age, BMI, and total testosterone levels). Moreover, AR repeat length was not associated with sperm retrieval rate. Standardized beta analyses demonstrated that testosterone levels, BMI, and age accounted for the largest proportion of phenotypic variability, whereas CAGn and GGCn repeat length had minimal roles. In untreated patients with KS, AR repeat length (CAGn and GGCn) appears to have a limited clinical impact compared with classical endocrine and metabolic determinants. These findings suggest that phenotypic variability in KS might be primarily driven by chromosomal aneuploidy and primary testicular dysfunction rather than AR repeat length.
Ferlin A et al., 2006 · Clinical endocrinology
Androgens and a functioning androgen receptor (AR) are essential for development and maintenance of the male phenotype and spermatogenesis. Consistent with this, mutations in the AR gene cause a variety of defects related to androgen insensitivity, ranging from complete feminization to phenotypic males with infertility. The aim of his study was to analyse the prevalence of AR gene mutations in male infertility and to clarify the genotype-phenotype relation. Males with infertility were recruited consecutively at the Centre for Male Gamete Cryopreservation at the University of Padova from January 1996 to January 2005. One thousand five hundred and seventeen men with < 10 million sperm/ml and 310 age-matched normozoospermic controls. Screening for AR gene mutation was done by DHPLC and sequencing, and reproductive hormone concentrations were measured. We found 20 mutations in 26 of 1517 patients (1.7%) and no mutations in controls. A high number of mutations localized in exon 1 of the AR gene coding for the transactivation domain of the protein. Of 20 mutations, 7 represent novel mutations. With respect to men without AR mutations, subjects with AR mutations have lower ejaculate volume, higher testosterone levels, higher oestradiol levels, and higher androgen sensitivity index. However, the ranges for these variables were highly overlapping between men with and without AR gene mutations. Also clinical manifestations of AR mutations are not unique and 22 men had only spermatogenic impairment. AR gene mutations are quite frequent in unselected infertile men but no specific hormonal or clinical data could be used to preselect patients at risk of mutations.
Zuccarello D et al., 2008 · Clinical endocrinology
Mutations in the androgen receptor (AR) gene can cause the androgen insensitivity syndrome (AIS). For complete and severe partial AIS, well-characterized in vitro functional assays can be used for genotype-phenotype correlation; however, for mild forms of AIS, as associated with male infertility, experimental evidence is scarce or lacking. In particular, optimal in vitro functional tests informative about the genotype-phenotype relation have not been described. The objective of this study was to investigate the association among genotype and phenotype for AR mutations found in infertile males by conventional functional assays and additional in-depth studies performed with several gene reporters. To this aim, we selected four AR missense mutations associated with isolated male infertility (L547F and two novel mutations A474V and S650G) or partial AIS (Y571H). After introduction of the specific mutations in AR expression plasmid, we performed classical in vitro studies (Western immunoblotting, electrophoretic mobility shift assay, hormone-response curves) and transactivation assays with different reporter constructs (MMTV, Sc-ARU-TK, TAT-GRE- 2X, Slp-ARU-TK and PEM). Our results showed that standard functional tests provide sufficient information only for severe AR mutations, whereas for AR mutations found in mild AIS patients with male infertility, only an extensive analysis with different in vitro systems, and in particular with PEM promoter, can give information on the functionality of the AR and therefore on the pathogenicity of the mutations and on genotype-phenotype correlation.
