Background: Elevated human epididymis secretory protein 4 (HE4) serum levels have been widely investigated in patients with ovarian cancer. However, high levels of HE4 can be also found in other tumors and in renal fibrosis. To date, the HE4 assay manufacturer features the reference value only for the female pre- and post-menopausal population. The aim of this study was to determine the upper reference limit (URL) of HE4 in a well-defined and large cohort of healthy male individuals and investigate potential factors influencing HE4 levels in healthy subjects.

Methods: The study included 307 Italian healthy male individuals. HE4 was measured using a chemiluminescent assay (Abbott Laboratories, Wiesbaden, Germany). The URL was calculated using the non-parametric percentile method. Differences in HE4 concentrations according to age, estimated glomerular filtration rate (eGFR), free and bioavailable testosterone were also evaluated.

Results: The 97.5th percentile URL of serum HE4 in our study population was 57 pmol/L (90% CI). After stratifying subjects according to age, we found that the URL of HE4 was higher in older (> 50 years) than in younger subjects (18-30 years old), and overlapping with the URL in males from 31 to 50 years old (P=4.769e-16, r=0.44). A strong negative correlation between HE4 and eGFR was observed (P=8.412e-12, r=-0.38). Moreover, a statistically significant negative correlation was also found between HE4 and free and bioavailable testosterone.

Conclusion: This study determined the URL of HE4 in a large cohort of healthy male subjects. Our findings indicate that the HE4 age-dependent differences in males need to be taken into account. The definition of the HE4 URL in males and the correlation observed with eGFR and testosterone should foster the clinical use of HE4 beyond gynecologic cancer.

背景：在卵巢癌患者中广泛研究了人类附睾分泌蛋白4（HE4）血清水平的升高。但是，在其他肿瘤和肾纤维化中也可以发现高水平的HE4。迄今为止，HE4分析制造商仅针对女性绝经前后人群提供参考值。这项研究的目的是确定健康男性个体中定义明确的大型人群中HE4的参考上限（URL），并研究影响健康受试者HE4水平的潜在因素。

方法：该研究包括307名意大利健康男性。使用化学发光测定法（Abbott Laboratories，威斯巴登，德国）测量HE4。URL是使用非参数百分位数方法计算的。还评估了HE4浓度随年龄，估计的肾小球滤过率（eGFR），游离和可生物利用的睾丸激素的差异。

结果：在我们的研究人群中，血清HE4的97.5％URL为57 pmol / L（90％CI）。根据年龄对受试者进行分层后，我们发现，年龄较大（> 50岁）的HE4 URL高于年轻人（18-30岁），并且与31至50岁男性的URL重叠（P = 4.769e-16，r = 0.44）。观察到HE4和eGFR之间有很强的负相关性（P = 8.412e-12，r = -0.38）。此外，还发现HE4与游离和可生物利用的睾丸激素之间存在统计学上的显着负相关。

结论：本研究确定了一大批健康男性受试者中HE4的URL。我们的发现表明，需要考虑男性HE4年龄依赖性差异。男性中HE4 URL的定义以及与eGFR和睾丸激素的相关性应促进HE4在妇科癌症以外的临床应用。