This meta-analysis of 13 studies provides a descriptive synthesis of testicular characteristics, semen parameters, and reproductive hormone profiles in infertile men with testicular microlithiasis.
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Research Article
* These authors contributed equally
This meta-analysis of 13 studies provides a descriptive synthesis of testicular characteristics, semen parameters, and reproductive hormone profiles in infertile men with testicular microlithiasis.
Testicular microlithiasis (TM) is frequently observed in infertile men, but its clinical significance remains controversial. This study aimed to systematically summarize the testicular characteristics, semen parameters, and reproductive hormone profiles of infertile men with TM and to describe the differences across TM subtypes. A systematic literature search was conducted in PubMed, Embase, Cochrane Library, and Web of Science from inception to November 14, 2025. Eligible studies included infertile male patients with ultrasound-confirmed TM. Data on testicular history, semen parameters, and hormonal profiles were extracted. Pooled prevalence estimates or pooled mean values were calculated using fixed- or random-effects models. Subgroup analyses were performed based on TM classification: classical (CTM) and limited (LTM). Thirteen studies were included. The pooled prevalence estimates of cryptorchidism, testicular cancer, and varicocele in infertile men with TM were 10.0%, 7.0%, and 37.0%, respectively. The pooled prevalence estimates of cryptorchidism, testicular cancer, and varicocele in infertile men with TM were 10.0%, 7.0%, and 37.0%, respectively. The pooled mean sperm concentration was 20.17 × 106/mL. Subgroup analysis showed that CTM was associated with significantly lower sperm concentration than LTM (P = 0.042), whereas no significant differences were observed between CTM and LTM for sperm morphology or gonadotropin levels.. In conclusion, this meta-analysis provides a descriptive synthesis of clinical findings, semen characteristics, and endocrine profiles in infertile men with TM.
Testicular microlithiasis (TM) is an ultrasonographic finding characterized by multiple non-shadowing hyperechogenic foci within the seminiferous tubules, typically reflecting intratubular calcifications. The clinical significance of TM remains under debate, particularly because of its proposed association with testicular germ cell tumors (TGCTs)1. Although the prevalence of TM in the general male population is relatively low, usually reported to be less than 5%2,3, its prevalence appears to be higher among infertile men, with recent studies reporting rates exceeding 10%4. TM has also been reported in individuals with underlying testicular pathologies, including cryptorchidism, varicocele, and non-obstructive azoospermia, all of which are commonly considered clinically important in the evaluation of male infertility and testicular health5.
Among these conditions, cryptorchidism is a well-established risk factor for impaired spermatogenesis and TGCT, even after surgical correction6. Varicocele is recognized as the most common surgically correctable cause of male infertility, affecting approximately 35% to 40% of infertile men7,8. Despite these observations, the clinical role of TM remains controversial. It remains unclear whether TM serves as an independent marker of testicular pathology or reflects coexisting subclinical testicular disease. Additionally, the relationship between TM and semen parameters, particularly sperm concentration and morphology, remains equivocal. Some studies have reported poorer semen parameters in men with TM, whereas others have found no significant differences compared with controls9,10,11.
Beyond anatomical abnormalities and semen quality, reproductive hormones provide important information on testicular function and spermatogenic activity. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are widely used indicators of germ cell and Leydig cell function, and altered hormone levels may reflect changes in spermatogenesis or in regulation of the hypothalamic-pituitary-gonadal axis. Characterizing endocrine profiles may help clarify whether reproductive hormone patterns differ across TM subtypes or coexist with other testicular findings. Although several studies have evaluated reproductive hormone levels in infertile men with TM, the reported findings have been variable, and the overall endocrine characteristics of this population remain poorly defined12,13. In addition to differences in associated clinical and semen characteristics, TM has been categorized into limited TM (LTM) and classic TM (CTM) based on the number of microliths observed on ultrasound. However, the clinical relevance of this subclassification for reproductive characteristics or testicular pathology has not been systematically evaluated.
Despite increasing interest in the reproductive implications of TM, evidence regarding the clinical characteristics, semen parameters, and reproductive hormone profiles reported in infertile men with TM remains fragmented. In particular, coexisting testicular conditions, including cryptorchidism, varicocele, and testicular cancer, as well as semen and endocrine findings, have not been comprehensively synthesized in this population. Therefore, this systematic review and meta-analysis aims to provide a descriptive synthesis of testicular disorders, semen parameters, and reproductive hormone profiles reported in infertile men with TM. Additionally, we explored whether these characteristics differed between LTM and CTM subgroups.
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Search strategy and selection criteria
This study conducted a comprehensive literature search across four databases, including PubMed, Embase, Cochrane Library, and Web of Science, covering the period from database inception to November 14, 2025. The search strategy combined Medical Subject Headings (MeSH) and free-text terms related to male infertility and TM and was adjusted according to the indexing system of each database. Representative search terms included "testicular microlithiasis", "microlithiasis", " testicular", and "Infertility, Male". The complete search strategies are provided in Supplemental Table S1.
Studies were included if they met the following criteria: (1) the study population included male patients with infertility; (2) TM was diagnosed by scrotal ultrasound; and (3) the study was an observational study, including a case-control study, cohort study, or single-arm study reporting extractable data on infertile men with TM.
Studies were excluded if they met any of the following criteria: (1) duplicate publications; (2) non-clinical studies, including reviews, expert opinions, case reports, conference abstracts, summaries, letters, editorials, animal studies, etc.; (3) case series/individual cases, or studies that cannot be compared with non-TM controls; (4) studies for which the full text is unavailable or the data were incomplete and could not be extracted or converted; (5) articles not published in English.
Data collection
Two reviewers independently screened titles and abstracts to identify studies that met the inclusion criteria and then reviewed the full texts according to predefined inclusion and exclusion criteria. Disagreements were resolved through discussion or consultation with a third reviewer. For each included study, data were extracted using standardized forms, including first author, publication year, study design, study group, age, history of cryptorchidism, coexisting testicular conditions including testicular cancer and varicocele, presence of a control group, TM classification criteria, sperm concentration, percentage of normal sperm morphology, FSH level, and LH level. Semen parameters were extracted according to the WHO semen analysis criteria used in the original studies (WHO 1999 and WHO 2010)14,15.
Quality assessment
The methodological quality of the studies included was independently assessed by two reviewers using the Newcastle-Ottawa Scale (NOS) for observational studies. The NOS evaluates three main domains: selection of study groups (maximum 4 points), comparability of groups (maximum 2 points), and ascertainment of outcomes (maximum 3 points), with a total possible score of 9. Studies scoring ≥ 6 points were considered to have moderate to high quality. Any discrepancies in scoring were resolved through discussion or consultation by a third reviewer.
Outcome measures
The primary outcome included testicular history and coexisting testicular conditions, semen parameters, and reproductive hormone profiles. For each categorical outcome, including history of cryptorchidism, testicular cancer, and varicocele, data were extracted as event counts and total sample sizes and summarized as pooled prevalence estimates. For continuous outcomes, including sperm concentration, normal sperm morphology, FSH, and LH, data were extracted as means, standard deviations, and sample sizes and summarized as pooled mean values. Subgroup analyses were performed based on the number of microliths observed on ultrasound (LTM and CTM). LTM was defined as <5 microliths, whereas CTM was defined as ≥5 microliths on ultrasound, based on the Bennett classification adopted by the included studies16.
Statistical analysis
Meta-analyses were conducted using random-effects (RE) and fixed-effects (FE) models, calculating pooled prevalence estimates and pooled mean values, along with their 95% confidence intervals (CIs). Statistical heterogeneity was assessed using the I2 statistic, with I2 values of 25%, 50%, and 75% considered low, moderate, and high heterogeneity, respectively. For I2 > 50%, the RE model was used; for I2 < 50%, the FE model was used. Subgroup differences were assessed using interaction p-values. When more than three studies were included, funnel plots were used to qualitatively assess publication bias for each outcome. Egger’s and Begg’s tests were not performed because fewer than 10 studies were included in most analyses.
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Study details and demographics
A total of 684 records were initially identified through the database search. After screening and eligibility assessment, 13 studies published between 1998 and 2022 were included in the meta-analysis. The included studies covered multiple geographical regions, including Europe, Asia, the Middle East, and North America4,13,17,...
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To our knowledge, this is the first meta-analysis specifically focused on infertile men with TM that quantitatively synthesizes semen characteristics, coexisting testicular conditions, and reproductive hormone profiles. Compared with previous evidence syntheses that primarily focused on semen parameters, our study further extends the current evidence by providing pooled estimates of cryptorchidism, varicocele, testicular cancer, and reproductive hormone levels, together with subgroup analyses according to TM subtype
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The authors have no conflicts to disclose.
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| Cochrane Library | Cochrane | N/A | Database searched for eligible studies. |
| Embase | Elsevier | N/A | Database searched for eligible studies. |
| Medical Subject Headings (MeSH) | U.S. National Library of Medicine | N/A | Controlled vocabulary used in the search strategy. |
| Newcastle-Ottawa Scale (NOS) | N/A | N/A | Tool used to assess the methodological quality of observational studies. |
| PubMed | U.S. National Library of Medicine | N/A | Database searched for eligible studies. |
| Stata 17.0 | StataCorp LLC | N/A | Software used for statistical analysis. |
| Web of Science | Clarivate | N/A | Database searched for eligible studies. |
| WHO semen analysis criteria/manuals (1999 and 2010) | World Health Organization | N/A | Reference criteria used to extract semen parameters according to the versions reported in the original studies. |
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