Correlation between reproductive hormone levels and genetic abnormalities in patients with non-obstructive azoospermia and oligospermia

Introduction

The prevalence of male infertility has increased in recent decades due to changes in lifestyle, environmental factors, and work-related stress. Male infertility accounts for approximately half of all infertility cases, affecting up to 17.5% of couples of childbearing age worldwide (1,2). Tens of millions of couples worldwide are affected by infertility. The condition profoundly impacts the lives, careers, and finances of affected couples, especially in low- and middle-income countries (3).

Infertility is a disease of the reproductive system characterized by the failure to achieve a clinical pregnancy after at least 12 months of unprotected intercourse (4). The etiology of male infertility is highly heterogeneous, primarily encompassing spermatogenic dysfunction (manifesting as azoospermia and oligospermia), obstruction of the vas deferens, and sexual dysfunction. Notably, patients with spermatogenic dysfunction typically present with normal sexual function. Consequently, their etiological diagnosis relies heavily on semen parameter analysis combined with hormonal and genetic testing, including karyotype analysis and screening for Y-chromosome microdeletions, to identify underlying genetic abnormalities (5).

The homeostasis of the reproductive endocrine system forms the physiological foundation for spermatogenesis. Testicular spermatogenic function is highly dependent on the hormonal microenvironment. Within this intricate regulatory network, the hypothalamic-pituitary-gonadal axis plays a central role: for instance, follicle-stimulating hormone (FSH) directly acts on supporting cells to initiate and sustain spermatogenesis, while luteinizing hormone (LH) stimulates interstitial cells to synthesize testosterone (T), providing the essential localized hormone concentration required for meiosis. Disruption of hormonal secretion rhythms or receptor signaling at any stage may lead to arrest or collapse of spermatogenesis, manifesting as oligospermia or azoospermia (6,7).

Chromosomal karyotype abnormalities represent a significant genetic cause of male infertility, with their detection rate showing a significant positive correlation with the severity of spermatogenic failure. Among men with infertility, the incidence of chromosomal abnormalities is approximately 6%, with Klinefelter syndrome (47,XXY karyotype) being the most common numerical chromosomal abnormality (8,9). The azoospermia factor (AZF) on the long arm of the Y chromosome is critical for spermatogenesis. This region contains three non-overlapping loci, AZFa, AZFb, and AZFc, essential for sperm production. Deletions in one or more of these loci can significantly impair spermatogenesis and lead to infertility (10-12). Reported frequencies of Y chromosome microdeletions exhibit slight variations across different geographical regions and ethnic populations. The prevalence ranges from approximately 3% to 15% in men with azoospermia and from 6% to 8% in those with severe oligospermia. Among the various deletion types, AZFc deletions are consistently identified as the most common form (13,14).

This study aims to systematically review and analyze the chromosomal karyotype and Y chromosome microdeletion distribution characteristics in patients with oligospermia and azoospermia, quantitatively evaluating differences in the detection rates of genetic abnormalities across populations with varying degrees of spermatogenic failure. Additionally, it will thoroughly investigate the intrinsic relationship between serum reproductive hormones and the types of genetic defects. We present this article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0045/rc).

Methods

Study subjects

This article is a retrospective study. From May 2019 to October 2023, 7,890 patients who sought treatment and consultation at the Reproductive Center of Longgang District Maternity & Child Health Hospital, Shenzhen City, were enrolled in this study. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Research Ethics Committee of Longgang District Maternity & Child Health Hospital (No. LGFYKYXMLL-2024-40). All participants provided written informed consent.

All subjects underwent a standardized andrology clinical evaluation. The assessment included: (I) medical history collection, covering reproductive history, past medical history (cryptorchidism, genitourinary infections), potential exposure to spermatogenic toxins (exogenous hormones, chemoradiotherapy), and family genetic background; (II) physical examination, including anthropometric measurements and specialized assessment for testicular volume, epididymal nodules, absence of vas deferens, or beaded changes; (III) reproductive hormone profile analysis; (IV) auxiliary tests, including scrotal ultrasound, peripheral blood chromosome karyotyping, and Y chromosome microdeletion detection.

Inclusion criteria: underwent routine semen analysis meeting diagnostic criteria for oligospermia and azoospermia, along with reproductive hormone testing, AZF gene analysis, and chromosomal karyotyping.

Exclusion criteria: obstructive azoospermia; history of taking spermatogenesis-inhibiting medications or undergoing radiotherapy/chemotherapy; missing hormone or chromosomal test data; presence of identifiable female infertility factors.

Semen collection

Patients were instructed to abstain from sexual activity for 2 to 7 days before semen collection, which was performed by masturbation into a sterile 90-milliliter specimen cup. After the semen was liquefied, the sperm concentration was analyzed using an automated sperm quality analyzer (Beion SAS, Beijing, China). If no sperm were detected, the sample was centrifuged at 3,000 ×g for 10 minutes. Azoospermia was confirmed when no sperm were found in three or more samples. Severe oligospermia was defined as a sperm concentration of less than 5×10⁶/mL, while oligospermia was defined as a sperm concentration between 5×10⁶/mL and 15×10⁶/mL (15,16).

Reproductive hormones testing

A total of 2 mL of venous blood was collected from fasting patients for hormone testing. FSH, LH, T, prolactin (PRL), progesterone (PROG), and estradiol (E2) levels were measured using the Abbott USA ARCHITECT i2000 chemiluminescent immunoassay analyzer. Inhibin B (INHB) levels were determined by enzyme-linked immunosorbent assay using reagents from DSL Company, USA. All procedures were performed according to the manufacturer’s instructions, and blood samples were immediately separated from serum.

Detection of AZF microdeletions

Genomic DNA was extracted from 2 mL peripheral blood samples using a reagent from Zeesan, Xiamen, China. AZF gene detection was performed according to the manufacturer’s instructions (Tellgen, Shanghai, China). Six sequence-tagged sites loci (Y84, sY86, sY127, sY134, sY254, and sY255) within the AZFa, AZFb, and AZFc regions were selected based on the guidelines of the European Academy of Andrology and the recommendations of the European Molecular Genetics Quality Network (17). The sex-determining region Y and the zinc finger protein gene were internal controls.

Chromosome karyotyping

Conventional peripheral blood lymphocyte culture, collection, fixation, slide preparation, and G-banding techniques were used for karyotype analysis. A total of 5 mL of peripheral blood was collected from each individual. After processing, slides were fixed and prepared under controlled humidity and temperature conditions. G-banding staining was applied to cell chromosomes, and at least twenty metaphase images were captured using the Leica GSL120 automated karyotyping scanner. Five mitotic phases with well-distributed chromosomes and appropriate lengths were selected for karyotype analysis. Karyotypes were identified and described according to the International System for Human Cytogenetic Nomenclature 2020.

Statistical analysis

Data were analyzed using R statistical software version 4.3.0. Two independent sample t-tests were used for normally distributed data with homogeneity of variance, and results were expressed as mean ± standard deviation (SD). Categorical data were expressed as n (%), and Fisher’s exact test was used for analysis. Spearman correlation analysis was performed to assess the relationship between variables. A P value of <0.05 was considered statistically significant.

Results

Comparison of reproductive hormone levels

A total of 179 men were enrolled in the study and divided into four groups based on semen analysis: azoospermia (n=80), severe oligospermia (n=33), oligospermia (n=31), and healthy controls (n=35). Sperm concentration levels in the control group were significantly higher than those in the other groups (Figure 1A). PRL levels were significantly higher in the azoospermia and severe oligospermia groups compared to the control group (Figure 1B). FSH levels were significantly elevated in all infertility groups, and LH levels were different in the azoospermia and oligospermia groups (Figure 1C,1D). INHB levels were lower in the azoospermia and severe oligospermia groups (Figure 1E), while T levels were reduced in the azoospermia group (Figure 1F). No significant differences in PROG and E2 levels were observed between the groups (Table 1).

Figure 1 Comparison of reproductive hormone levels. (A) Sperm concentration was significantly lower in the infertility groups compared to the control group (P<0.05). (B) PRL concentration was slightly higher in the oligospermia group than in the control group, but the difference was not statistically significant. However, PRL levels were significantly higher in the azoospermia and severe oligospermia groups compared to the control group. (C) FSH concentration was markedly increased in the infertility groups. (D) LH concentrations were significantly higher in the azoospermia and oligospermia groups compared to the control group. (E) INHB concentrations were significantly lower in the azoospermia and severe oligospermia groups compared to the control group. (F) T concentration was significantly lower in the azoospermia group compared to the control group. FSH, follicle-stimulating hormone; INHB, inhibin B; LH, luteinizing hormone; PRL, prolactin; T, testosterone.

AZF microdeletion analysis

No AZF microdeletions were detected in the oligospermia or control groups. In the azoospermia and severe oligospermia groups, AZF microdeletions were more frequent than in the control group, although the difference was not statistically significant (P>0.05). Among the 33 patients with severe oligospermia, 3 cases (9.09%) of AZF microdeletions were identified, all involving the AZFc region. Among 80 patients with azoospermia, 7 cases (8.75%) of AZF microdeletions were detected, including 4 cases (5.00%) of AZFc deletion, 2 cases (2.50%) of AZFb + c deletion, and 1 case (1.25%) of AZFa + b + c deletion (Table 2).

Chromosome karyotyping analysis

No karyotypic abnormalities were detected in the control, oligospermia, and severe oligospermia groups. A statistically significant difference (P<0.05) was observed in the incidence of abnormal karyotypes between the azoospermia group and the control group. Abnormal karyotypes were found in 13 of the 80 azoospermia patients (16.25%). Among these, 9 cases (11.25%) had a 47,XXY karyotype. Other abnormalities included 1 case of 48,XXYY,inv(Jeny2)(p11.2q13), 1 case of 46,X,del(Y)(q11.23), 1 case of 47,XXY [21]/46,XY mosaic [30], and 1 case of 46,XX sex reversal (Table 3, Figure 2).

Figure 2 Chromosomal karyotypes in the azoospermia group. Chromosomal karyotypes identified in the azoospermia group included: (A) 47,XXY; (B) 48,XXYY,inv(Jeny2)(p11.2q13); (C) 46,X,del(Y)(q11.23); (D) mosaic 47,XXY and 46,XY; (E) sex reversal male with 46,XX karyotype; (F) normal healthy control with a 46,XY karyotype. Red arrows indicate the specific locations on the karyotype where the four abnormal chromosomes (A-D) are located.

Correlation analysis

Principal component analysis (PCA) revealed significant differences in hormone levels between the azoospermia/severe oligospermia and the control/oligospermia groups (Figure 3). The study demonstrates a robust correlation between alterations in sperm concentration and reproductive hormone levels. Furthermore, the prevalence of chromosomal abnormalities and AZF gene deletions increases as sperm concentration declines, potentially contributing to the observed hormonal imbalances in these groups. No notable changes in these indicators were observed in the oligospermia and control groups, and their correlation with age was insignificant (Table 4, Figure 4).

Figure 3 PCA of reproductive hormones among the four groups. PCA reveals that reproductive hormone levels in the azoospermia and severe oligospermia groups differ significantly from those in the control group. PCA, principal component analysis.

Figure 4 Correlation analysis of reproductive hormones, chromosomal karyotypes, AZF genes, and sperm concentration. Analysis indicates that reduced levels of T and INHB, accompanied by elevated levels of PRL, LH, and FSH, were primarily observed in the azoospermia and severe oligospermia groups. In contrast, PROG and E2 levels showed only a weak correlation with sperm concentration. Furthermore, as sperm concentration decreases, the incidence of chromosomal abnormalities and AZF gene deletions gradually increases. In the oligospermia group and the control group, no significant changes were observed in these indicators, and their correlation with age was minimal. AZF, azoospermia factor; E2, estradiol; FSH, follicle-stimulating hormone; INHB, inhibin B; LH, luteinizing hormone; PRL, prolactin; PROG, progesterone; T, testosterone.

Discussion

Through a systematic analysis of 179 male infertility patients from southern China, this study constructed a region-specific three-dimensional association map of semen parameters-reproductive hormones-genetic defects. Although the pathogenicity of AZF microdeletions and chromosomal abnormalities is well established, the novelty of this study lies in revealing the intricate interaction patterns between these genetic factors and endocrine phenotypes in a specific regional population. Our data indicate that in the Southern Chinese population, azoospermia and severe oligospermia are characterized not only by a drastic decline in sperm concentration but are also accompanied by unique hormonal profile alterations and a high prevalence of specific genetic subtypes (primarily AZFc and 47,XXY). These region-specific findings fill a gap in the existing literature regarding the molecular epidemiological characteristics of male infertility in Southern China and provide empirical evidence for the development of targeted regional clinical screening strategies.

Reproductive hormone testing is critical in the diagnosis of male infertility and provides valuable insight into the underlying causes of azoospermia and oligospermia. FSH, secreted by the pituitary gland, plays a critical role in Sertoli cell function in the testis, and its levels may reflect Sertoli cell maturity and activity (18). INHB, produced by cells in the reproductive system, is an essential marker for evaluating spermatogenesis and vas deferens function (19). Previous studies have reported a negative correlation between serum INHB and FSH levels in adult men. Low INHB levels are more sensitive than high FSH levels in detecting testicular damage. Combining these two markers increases the diagnostic sensitivity and specificity (20).

Although our findings are consistent with those reported in Western populations (21,22), the increases in FSH and decreases in INHB appear to be more pronounced in our study and show a stronger correlation with sperm concentration. This difference may be attributed to differences in ethnic and genetic backgrounds, or to a specific phenotype resulting from the high prevalence of chromosomal abnormalities in this patient cohort.

LH plays a critical role in the proliferation and maturation of Leydig cells and stimulates the production of T, which is essential for male secondary sexual characteristics, genital development, and spermatogenesis (23,24). Under normal circumstances, LH and T are regulated by a negative feedback mechanism, exhibiting an inverse relationship: when testicular failure leads to impaired T synthesis, LH levels rise compensatorily. In this study, the non-obstructive azoospermia group exhibited significantly elevated LH levels, accompanied by significantly reduced T levels, consistent with severe Leydig cell dysfunction and primary testicular failure. However, the hormonal profile in oligospermia is more complex. Patients with hypogonadotropic oligospermia or asthenospermia present with normal or low LH levels (due to hypothalamic-pituitary axis dysfunction); therefore, it cannot be simply assumed that LH levels are elevated in all patients with oligospermia (25,26). Furthermore, we observed elevated PRL levels in the azoospermia and severe oligospermia groups, which may be related to neuroendocrine dysregulation associated with severe gonadal hypofunction and is consistent with previous reports that hyperprolactinemia inhibits spermatogenesis (27).

Regarding genetic etiology, Y-chromosome microdeletions represent the second most common cause of male infertility, primarily attributed to the critical role of genes within the AZF regions in regulating spermatogenesis (28). In our study, the prevalence of AZF microdeletions was 9.09% in the severe oligospermia group and 8.75% in the azoospermia group. These rates are slightly higher than those reported in South China (6.69% and 7.71%, respectively) (29) but align closely with data from Northeast China (30). Such geographical discrepancies may reflect distinct genetic backgrounds across different populations, although variations in sample size and selection bias among studies cannot be excluded. Regarding the distribution of deletion types, the AZFc region, rich in palindromic sequences, exhibits heightened susceptibility to non-allelic homologous recombination, making it the predominant deletion hotspot (31). Consistent with this mechanism, all detected deletions in our cohort were of the AZFc type, with no isolated AZFa or AZFb deletions observed. While this distribution pattern mirrors reports from some Western populations, the overall prevalence of microdeletions in our study was significantly lower than that reported in Western cohorts (11). This finding further suggests that race-specific genetic backgrounds may play a pivotal role in the formation of Y-chromosome deletion hotspots and population susceptibility.

Although this study observed that AZFc deletions are predominant in infertile men, we must acknowledge that the correlation between Y-chromosome microdeletions and testicular histopathological phenotypes is not always linear. Previous studies have shown that the same type of AZFc deletion can be associated with a wide range of pathological changes, ranging from severe azoospermia to mild oligospermia. This mismatch between genotype and phenotype suggests that AZF status alone may not be sufficient to fully determine the histological fate of the testis. However, deletions in the AZFa and AZFb regions carry a very poor prognosis and are highly correlated with severe phenotypes (32).

Chromosomal abnormalities, as a key genetic cause of male infertility, exhibit significant pathogenic characteristics, particularly in the azoospermia population. Although the detection rate of karyotype abnormalities in this study (16.25%) was slightly lower than the 22.97% reported in previous literature (33), this discrepancy may stem from limitations in sample size; small cohorts often fail to fully capture the population distribution of chromosomal abnormalities. Nevertheless, the findings are sufficient to reflect the high prevalence of such abnormalities among patients with azoospermia. Among the spectrum of abnormalities, Klinefelter syndrome (47,XXY) was the most common cytogenetic alteration, accounting for 11.25%. The extra X chromosome leads to hyalinization of the seminiferous tubules and impaired interstitial cell function through a gene dosage effect. This finding is highly consistent with the conclusions of studies on the pathological association between this karyotype and hypogonadism (34). Furthermore, the detection of rare abnormalities such as 48,XXYY, Y-chromosome long-arm deletions, inversions, and 46,XX gender reversal syndrome (35) not only expanded the spectrum of genetic causes of male infertility but also revealed multidimensional pathogenic mechanisms ranging from sex chromosome aneuploidy to autosomal translocations, and from gene copy number variations to abnormalities in the sex-determination pathway, highlighting the high heterogeneity of the genetic background in male infertility. These findings collectively underscore the necessity of systematically conducting chromosomal karyotyping in clinical practice. This approach not only facilitates precise identification of the causes of infertility but also provides critical evidence for genetic counseling, the selection of assisted reproductive technologies, and the assessment of genetic risks in offspring.

However, this study has several limitations. First, the sample size was relatively small, particularly in the subgroup with specific genetic abnormalities, which limited the statistical power to detect significant differences in variants. As a result, some of the comparisons of AZF did not reach statistical significance, and subgroup analyses could not be performed. Second, the retrospective study design does not allow for causal inferences regarding the temporal relationship between hormonal changes and gene expression. Third, this study focused on a population from a specific geographic region (southern China); therefore, the generalizability of its results to other regions remains to be verified. Future multicenter studies with larger sample sizes and longitudinal follow-up are needed to refine the predictive models.

Conclusions

In summary, abnormalities in reproductive hormones are more pronounced in patients with oligospermia, suggesting that endocrine dysfunction may be a primary pathogenic factor. In contrast, the prevalence of genetic abnormalities (AZF microdeletions and chromosomal abnormalities) is higher in the severe oligospermia and azoospermia groups, supporting the potential value of combining genetic testing with hormonal analysis for these patients prior to considering assisted reproductive technology.

However, given the limitations of this study—including a relatively small sample size, the absence of standardized clinical screening criteria, and a retrospective study design—these findings should be interpreted with caution. Such studies must adhere to rigorous methodological standards to validate these patterns and establish clear clinical screening protocols. Until then, the combined use of these diagnostic methods should be considered on a case-by-case basis according to individual clinical presentations, rather than being regarded as a universal requirement.

Acknowledgments

We would like to thank the other members of the Department of Reproductive Center of Longgang District Maternity & Child Healthcare Hospital of Shenzhen City (Longgang Maternity and Child Institute of Shantou University Medical College) for their help.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0045/rc

Data Sharing Statement: Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0045/dss

Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0045/prf

Funding: This research was supported by a grant from the Medical and Health Technology Research Project, Longgang District of Shenzhen City (No. LGWJ2023-[67]).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-1-0045/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Research Ethics Committee of Longgang District Maternity and Child Health Hospital (No. LGFYKYXMLL-2024-40). All participants provided written informed consent.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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