Determination of the Upper Reference Limit of Human Epididymis Secretory Protein 4 (HE4) in Healthy Male Individuals and Correlation with Renal and Fertility Markers.

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.