Male Fertility · Semen Analysis
Abstract
Study Question
Could sperm telomere length (STL) represent a novel parameter and biomarker of sperm quality?
Summary Answer
STL is associated with standard semen quality parameters and, more importantly, it is significantly associated with levels of DNA fragmentation and sperm protamination.
What Is Known Already
Telomeres are fundamental for genome integrity. Recent studies have demonstrated that STL increases with age and men with oligozoospermia have shorter sperm telomeres than normozoospermic men.
Study Design, Size, Duration
Cohort study conducted from September 2014 to June 2015 on 100 subjects with normal standard semen parameters.
Participants/Materials, Setting, Methods
STL was measured indirectly by quantitative polymerase chain reaction using telomere/single-copy gene ratio, sperm DNA fragmentation by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling assay and protamination by aniline blue staining. Data were analyzed for determining the relationships between STL, standard semen parameters and DNA fragmentation and protamination.
Main Results and the Role of Chance
Among standard semen parameters, STL was positively associated with progressive motility (P = 0.004) and vitality (P = 0.007). STL was significantly and negatively associated with sperm DNA fragmentation (P = 0.001) and significantly and positively associated with protamination (P = 0.002). The role of chance was limited and the findings have biological relevance and a pathophysiological explanation.
Limitations, Reasons for Caution
For the present study, we deliberately selected only men with normozoospermia to better analyze whether STL might represent a biomarker of sperm quality beyond traditional sperm parameters. Additional studies in proven fertile men with normal sperm parameters are needed.
Wider Implications of the Findings
The measurement of STL is a simple and rapid method that offers further information about the quality of sperm. The results of this study demonstrate that STL could be considered as an additional sperm parameter and opens new perspectives in the evaluation of the infertile male. Additional studies will clarify the significance of this parameter also as a prognostic biomarker in assisted reproduction.
Study Funding/Competing Interests
No external funding was either sought or obtained for this study. There are no conflicts of interest to be declared.
Topics
By this author
Semen Analysis · Sperm Function Testing
Preimplantation genetic testing for male factor infertility: lights and shadows
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.
Male Factor Causes · Hormonal Causes
Pathophysiology-Based Classification of Male Infertility: Evidence from an 800-patient Prospective Cohort
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.
Semen Analysis · Sperm Function Testing
Beyond semen analysis: in men with normal semen parameters telomere attrition and oxidative imbalance distinguish those fertile from those with infertility
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.
Semen Analysis · Reference Standards
Semen Quality in Transgender Individuals Seeking Fertility Preservation
Ponce MR et al., 2026 · Andrology · Free full text on PubMed Central
Transgender individuals assigned male at birth (AMAB) may choose to preserve their fertility prior to starting gender-affirming hormone therapy (GAHT). However, limited data exist regarding the baseline reproductive and hormonal characteristics of this population before and after GAHT. To characterize semen quality and hormonal profiles in transgender AMAB individuals prior to GAHT and compare findings with cisgender men and with transgender individuals who discontinued GAHT for at least 3 months. This retrospective study included transgender AMAB individuals from two tertiary andrology centers who underwent sperm cryopreservation before GAHT initiation (treatment-naïve group). Clinical evaluation included anthropometric measures, testicular volume assessment, varicocele detection, and sex hormone measures. Semen parameters were analyzed according to WHO criteria and compared with those of cisgender men and previously treated transgender individuals. Thirty-two treatment-naïve transgender AMAB individuals were included. Hormonal parameters were generally within reference ranges. Only 46.9% of treatment-naïve individuals met WHO criteria for normozoospermia, compared with 75.5% of cisgender controls. Compared with nine previously treated individuals, estradiol levels were higher and seminal volume lower. A higher frequency of seminal abnormalities was observed, although not statistically significant. A substantial proportion of treatment-naïve transgender AMAB individuals exhibited impaired semen parameters prior to GAHT initiation. Prior GAHT exposure showed a trend toward poorer semen quality. These findings support early fertility counseling and preservation in transgender individuals prior to GAHT initiation.
Related research
Semen Analysis · Reference Standards
Lab-based semen parameters as predictors of long-term health in men-a systematic review
Nedelcu S et al., 2024 · Hum Reprod Open · Free full text on PubMed Central
Can semen parameters predict long-term health outcomes in men? There is a lack of evidence to suggest a higher risk of comorbidities in men with poor semen concentration. Male infertility has been long associated with a higher mortality risk and possibly higher chance of developing comorbidities but there has been less focus on semen analysis as a potential predictive factor. We searched PubMed/MEDLINE, EMBASE, and EBM databases from inception to December 2023. MESH term strategy: heading 1 ('OR', semen analysis, sperm count, sperm parameter*, male infertility, azoospermia, aspermia, oligospermia, teratozoospermia, asthenozoospermia) 'AND' heading 2 ('OR', morbidity, mortality, diabetes, cancer, cardiovascular, death, hypertension, stroke, long-term health). We included all studies that analyzed the risk of mortality and/or future development of comorbidities in men with at least one semen analysis. Case series and reviews were excluded. A narrative synthesis was done for all studies and meta-analysis where possible. Odds ratio (ORs) (95% CI, P-value) were calculated for all men with one suboptimal semen parameter and associated with the risk of a particular outcome. The risk of bias was assessed with QUADAS-2. MAIN Twenty-one studies were finally included. There was either a high or unclear risk of bias in all studies. The results only allowed for meta-analysis on categories of sperm concentration. We found a 2-fold increase in mortality risk in azoospermic men compared to oligospermic (OR 1.96, 95% CI: 1.29-2.96) and normozoospermic (OR 2.00, 95% CI: 1.23-3.25) groups, but not in oligospermic compared to normozoospermic (OR 1.04, 95% CI: 0.52-2.09). There was no difference in risk of cardiovascular disease in any of the sperm concentration groups (azoospermic-oligospermic OR 0.94, 95% CI: 0.74-1.20, azoospermic-normozoospermic OR 1.11, 95% CI: 0.71-1.75, and oligospermic-normozoospermic OR 1.12, 95% CI: 0.80-1.55). OR for diabetes in azoospermic men was higher only compared to oligospermic (OR 2.16, 95% CI: 1.55-3.01). The risk of all-site cancer was higher in azoospermic men compared to oligospermic (OR 2.16, 95% CI: 1.55-3.01) and normozoospermic (OR 2.18, 95% CI: 1.20-3.96). Only azoospermic men might be at higher risk of testicular cancer when compared to men with normal sperm concentration (OR 1.80, 95% CI: 1.12-2.89). LIMITATIONS Although our pooled analysis shows an increased risk of mortality and all-site cancer risk in azoospermic men, the results show a lack of evidence to suggest a higher risk of comorbidities in men with poor semen concentration. Given the limited available data, the nature of the studies, and the high risk of bias, the results should be interpreted with caution. There is not enough data to confirm the usability of semen analysis as a predictor of poor long-term health in men, especially within the general population. No funding was obtained for this study. A.M. has received funding from Merck Serono, Ferring, Gedeon Richter, Pharmasure, and Cook Medical to attend medical conferences; has been a participant in an advisory board for Ferring; and has given an invited lecture for a Merck Serono advisory board. S.N. has received funding for medical conference attendance from Ferring and Cook Medical. PROSPERO No. CRD42024507563.
Male Endocrine and Genetic Factors · Genetic Causes of Male Infertility
Novel insights on testicular volume and testosterone replacement therapy in Klinefelter patients undergoing testicular sperm extraction. A retrospective clinical study
Garolla A et al., 2018 · Clinical endocrinology
To investigate whether sperm recovery is related to clinical features, hormone parameters and testosterone replacement therapy (TRT) in patients with Klinefelter syndrome (KS). This study provides three interesting insights: (i) the probability to retrieve sperm is not related to testicular volume; (ii) TRT does not affect sperm retrieval rate (SRR); and (iii) reduced levels of LH and FSH represent a negative predictor of sperm retrieval in patients with TRT. Classical KS shows a karyotype with one extra X chromosome in all of somatic cells and clinical manifestations characterized by hypergonadotropic hypogonadism and infertility. STUDY DESIGN, We performed a retrospective cohort study. Data from 111 consecutive KS azoospermic patients undergoing testicular sperm extraction (TESE) were collected from 2005 to 2016. PARTICIPANTS/MATERIALS, Data on anthropometric parameters, reproductive hormones and testicular volumes were collected. SRR was related to clinical characteristics and compared between TRT and untreated patients. MAIN A total of 38 patients (34.2%) had successful sperm recovery. The comparison of clinical characteristics did not differ between patients with and without sperm recovery. Sperm retrieval was successful also in subjects with smaller testes. The comparison of SRR in patients with or without TRT was not different (33.3% vs 34.6%). In TRT group, LH and FSH levels were significantly lower in subjects with no sperm retrieval (P values, respectively, <.05 and <.001). LIMITATIONS Well-designed controlled studies are necessary to confirm these data aimed to set the best therapeutic approach for fertility management in hypogonadal patients with nonmosaic KS. Age at TESE, anthropometric measures, testis volume, sex hormones levels and semen parameters are not predictive parameters of SRR. Among TRT patients, reduced gonadotropin is related to failure in sperm retrieval.
Semen Analysis · Reference Standards
Male fertility and reduction in semen parameters: a single tertiary-care center experience
Milardi D et al., 2012 · International journal of endocrinology · Free full text on PubMed Central
Background. Infertility is both a clinical and a public problem, affecting the life of the couple, the healthcare services, and social environment. Standard semen analysis is the surrogate measure of male fertility in clinical practice. Objective. To provide information about the relationship between semen parameters and spontaneous conception. Methods. We evaluated retrospectively 453 pregnancies that occurred among 2935 infertile couples evaluated at an infertility clinic of a tertiary-care university hospital, between 2004 and 2009. Results. Normal semen analysis was present only in 158 patients; 295 subfertile patients showed alterations in at least one seminal parameter. A reduction in all seminal parameters was observed in 41 patients. Etiological causes of male infertility were identified in 314 patients. Conclusion. Our data highlights the possibility of a spontaneous conception with semen parameters below WHO reference values. Therefore, we support the importance of defining reference values on a population of fertile men. Finally, we analyzed the related ethical issues.
Male Factor Causes · Lifestyle and Environment
Obesity leads to higher risk of sperm DNA damage in infertile patients
Dupont C et al., 2013 · Asian journal of andrology · Free full text on PubMed Central
There has been a growing interest over the past few years in the impact of male nutrition on fertility. Infertility has been linked to male overweight or obesity, and conventional semen parameter values seem to be altered in case of high body mass index (BMI). A few studies assessing the impact of BMI on sperm DNA integrity have been published, but they did not lead to a strong consensus. Our objective was to explore further the relationship between sperm DNA integrity and BMI, through a 3-year multicentre study. Three hundred and thirty male partners in subfertile couples were included. Using the terminal uridine nick-end labelling (TUNEL) assay, we observed an increased rate of sperm DNA damage in obese men (odds ratio (95% confidence interval): 2.5 (1.2-5.1)).
Male Fertility › Semen Analysis › Sperm Function Testing
PMID 27052502 27052502 DOI 10.1093/humrep/dew061 10.1093/humrep/dew061 Rocca et al. 2016, Rocca 2016