Zonulin Levels in Varicocele Patients

Varicocele is one of the most common causes of male infertility and is associated with impaired spermatogenesis through multiple mechanisms, including oxidative stress, inflammation, and disruption of testicular microcirculation. Zonulin, a physiological regulator of epithelial tight junctions, has been proposed as a biomarker of increased intestinal permeability and systemic inflammation. However, the relationship between serum and seminal plasma zonulin levels and varicocele in infertile men has not been fully investigated.

This prospective observational study was designed to evaluate serum and seminal plasma zonulin levels in infertile men with clinically diagnosed varicocele and compare them with those in infertile men without varicocele. The study was also designed to examine the association between zonulin concentrations and conventional semen parameters, including semen volume, sperm concentration, total sperm count, progressive motility, total motility, and normal sperm morphology.

A total of 119 infertile men presenting to the Urology outpatient clinic between December 2022 and May 2023 were enrolled. Participants were assigned to groups according to the presence or absence of clinically diagnosed varicocele. Patients with systemic diseases, active infections, tobacco or cannabis use, use of medications known to affect semen parameters, abnormal body mass index, or evidence of genital tract infection were excluded. Serum and seminal plasma samples were collected on the day of semen analysis, and zonulin concentrations were measured using enzyme-linked immunosorbent assay (ELISA).

The primary objective was to compare serum and seminal plasma zonulin levels between infertile men with and without varicocele. Secondary objectives were to evaluate the association between zonulin concentrations and conventional semen parameters.

Inclusion criteria

• Male patients aged 18 to 50 years.
• Infertility requiring semen analysis.
• No history of systemic disease.
• Non-smokers and non-cannabis users.
• No use of medications that could affect semen parameters within the previous 3 months.
• Body mass index (BMI) between 20 and 30 kg/m².

Exclusion criteria

• Presence of any chronic systemic disease.
• Signs or symptoms of active infection.
• Tobacco smoking or cannabis use.
• Illicit drug use.
• Use of medications that could affect semen parameters within the previous 3 months.
• Clinical findings suggestive of prostatitis or urethritis (elevated white blood cell count on semen analysis).
• Body mass index (BMI) <20 kg/m² or >30 kg/m².
• Leukocyte concentration >1 × 10⁶ cells/mL in semen, indicative of a possible genital tract infection.