Spermatic Vein Blood Reveals Hidden Inhibin B Drop in Varicocele

Men with a varicocele—an enlargement of the veins inside the scrotum—can show normal hormone levels on a standard blood test drawn from the arm, yet a study published in BMC Urology suggests that the picture looks very different when blood is sampled directly from the vein draining the affected testicle. In a paired observational study of 76 young men, researchers found that inhibin B, a hormone produced by Sertoli cells in the testes, was markedly lower in the affected spermatic vein than in the peripheral circulation, even though peripheral inhibin B values were normal in every participant. The finding points to a localized testicular change that conventional blood testing cannot detect.

The study, led by Chen Xiao with co-authors including Jing Zhang, Shoubo Zhang, Tingfa Qiu, Xi Chen, Wenjie Luo, Xudong Zhang and Yuejun Xu, was published on 23 October 2026 as an open access research article. The authors prospectively enrolled men aged 18 to 28 years who had clinical grade 2 or 3 unilateral varicocele, meaning the distended veins were moderate to pronounced on physical examination, and who were scheduled to undergo microsurgical varicocelectomy, the standard microsurgical repair of the abnormal veins. To qualify for the study, each participant also had to have normal peripheral inhibin B and testosterone levels, which ensured that any differences found in the spermatic vein could not simply reflect an already visible systemic hormone deficiency.

During the operation, the surgeons took a direct sample of blood from the affected internal spermatic vein and compared it with a sample of peripheral venous blood from the same patient. This paired design is the study’s central strength, because each man served as his own control and the two samples were analyzed for the same panel of hormones: inhibin B, testosterone, estradiol, follicle-stimulating hormone, luteinizing hormone and progesterone.

The results revealed what the authors describe as a hormone dissociation phenomenon. Inhibin B in the affected spermatic vein averaged 91.4 pg/mL with a standard deviation of 71.2, while peripheral inhibin B averaged 217.8 pg/mL with a standard deviation of 127.6, a difference that reached statistical significance at p < 0.0001. Because inhibin B is secreted by Sertoli cells, the support cells that nurture developing sperm, a local deficit of this hormone in the effluent blood is consistent with impaired Sertoli cell function confined to the affected side.

The same dissociation ran in the opposite direction for the sex steroid hormones. Testosterone in the affected vein averaged 450.0 nmol/l compared with 26.2 nmol/l in peripheral blood, and estradiol averaged 276.0 ng/L compared with 35.2 ng/L, both differences also significant at p < 0.0001.

Beyond the paired comparison, the researchers examined whether the local inhibin B deficit tracked with measures of varicocele severity. They found significant negative correlations between affected-vein inhibin B and three independent severity parameters: venous diameter measured on ultrasound (r = -0.412, p = 0.0052), ultrasound grade of the varicocele (r = -0.317, p = 0.0427) and clinical grade assessed on physical examination (r = -0.286, p = 0.0483). The negative direction of these correlations means that the more dilated the veins and the more advanced the clinical grade, the lower the inhibin B concentration in the draining vein. The correlation coefficients are moderate, so the associations explain only part of the variability, but their consistency across three different severity measures strengthens the pattern.

The authors propose a potential model of selective Sertoli cell dysfunction driven by venous hypertension, the elevated pressure within the dilated spermatic veins that characterizes varicocele. The study is explicitly framed as suggesting this model rather than proving it, and the authors note that affected-vein inhibin B warrants further evaluation as a candidate marker rather than serving as an established diagnostic test.

The practical implication highlighted by the study is the limitation of relying solely on peripheral blood testing to assess testicular endocrine function in varicocele. The authors emphasize that this observation identifies a blind spot in conventional peripheral indicators and motivates further research into whether spermatic vein sampling or related approaches could add information in selected cases.

Several caveats frame the findings. The study enrolled a specific population—young men with moderate to severe unilateral varicocele and normal peripheral hormones who were already undergoing surgical repair—so the results apply to that group and cannot be generalized to all varicocele patients, to men with milder disease, or to those with abnormal peripheral hormone levels. The design is observational and cross-sectional, capturing hormone concentrations at a single time point, which means it can document associations but cannot establish that venous hypertension causes the Sertoli cell changes or that correcting the varicocele reverses them. Inhibin B in the spermatic vein also remains an invasive research measurement rather than a clinical tool. Within those limits, the study offers a concrete physiological observation: the testicular venous effluent in varicocele carries a hormone signature that peripheral blood does not show, and that signature scales with the anatomical severity of the venous abnormality.

Subject of Research: Local inhibin B depletion in the spermatic vein of varicocele patients with normal peripheral hormone levels

Article Title: Reduced spermatic venous inhibin B in varicocele: a paired observational study suggesting possible selective sertoli cell dysfunction

Article References: Xiao, C., Zhang, J., Zhang, S., Qiu, T., Chen, X., Luo, W., Zhang, X., & Xu, Y. (2026). Reduced spermatic venous inhibin B in varicocele: a paired observational study suggesting possible selective sertoli cell dysfunction. BMC Urology. https://doi.org/10.1186/s12894-026-02447-0

Image Credits: AI Generated

DOI: 10.1186/s12894-026-02447-0

Keywords: varicocele, inhibin B, Sertoli cells, spermatic vein, testosterone, estradiol, venous hypertension, microsurgical varicocelectomy, peripheral blood testing, testicular endocrine function, hormone dissociation, BMC Urology