Serum 17-Hydroxyprogesterone is a Potential Biomarker for Evaluating Intratesticular Testosterone

Intratesticular testosterone is essential for spermatogenesis and can only be reliably measured with invasive testicular sampling. Previous studies have demonstrated good correlation between intratesticular testosterone and serum 17-hydroxyprogesterone (17-OHP) in men treated with human chorionic gonadotropin. Based on this observation we hypothesized that we can use serum 17-OHP as a serum biomarker for evaluating intratesticular testosterone in men receiving medications that alter serum testosterone.

Initially, we conducted a cross-sectional analysis of men with a single serum 17-OHP evaluation from July 2018 to March 2019. We followed this with a prospective analysis from July 2018 to October 2019 with evaluation of 140 men including fertile controls, and those receiving treatments that alter serum testosterone at baseline and after 3 months of therapy. According to the data distribution, we reported the median and interquartile ranges, and used the Mann Whitney U or Wilcoxon tests.

In the initial cross-sectional analysis of 93 men, a total of 30 men received treatments that increase or maintain intratesticular testosterone concentrations, such as clomiphene citrate and/or human chorionic gonadotropin; 21 men received treatments that suppress intratesticular testosterone concentrations (various exogenous testosterone replacement therapy formulations) and 42 fertile men with normal serum testosterone (greater than 300 ng/dl) were used as control. We demonstrated that serum testosterone levels were within normal range among men receiving the various therapies. In contrast, we found that serum 17-OHP was undetectable in men who received exogenous testosterone replacement therapy, as opposed to men receiving human chorionic gonadotropin and/or clomiphene citrate or fertile controls (p <0.05). In the prospective evaluation that ensued, 17-OHP values decreased in the 21 men who received testosterone replacement therapy (47.5 [21-70] to 13.5 [10-23] ng/dl, p <0.05). Conversely, 17-OHP increased in the 55 men who received human chorionic gonadotropin and/or clomiphene citrate when compared to their baseline levels (42 [24-72] to 88 [61-135] ng/dl, p <0.05).

Serum 17-OHP appears to be a reliable serum marker for intratesticular testosterone levels and could potentially be used to titrate or change medications that alter intratesticular testosterone.