Serum Inhibin—Not a Cause of Low Testosterone Levels in Hypogonadal Prostate Cancer?

Objectives

High-grade prostate cancer is associated with low serum testosterone levels, which generally recover after radical prostatectomy. The cause of this low testosterone level is unclear, and it has been hypothesized that cancer cells produce a factor that disturbs the pituitary-gonadal axis. Inhibin is a hormone that has a negative feedback effect on this axis. The aim of this study was to investigate the role of serum inhibin in patients with prostate cancer.

Methods

The serum hormone levels of the pituitary-gonadal axis, including inhibin levels, in patients with prostate cancer were compared with those in patients with benign prostatic hyperplasia. Testosterone levels of less than 3 ng/mL were classified as hypogonadal. Prostate cancer was classified according to Gleason score as high grade (Gleason score 7 to 10) or low grade (Gleason score 2 to 6).

Results

A total of 196 men (126 with prostate cancer and 70 with benign prostatic hyperplasia) were entered into the study. The serum inhibin levels did not differ significantly between the patients with benign prostatic hyperplasia and those with prostate cancer (150.0 versus 131.75 pg/mL, P = 0.062), between men with hypogonadal and eugonadal disease (143.0 versus 146.5 pg/mL, P = 0.573), or between those with low-grade and high-grade cancer (151.5 versus 146.0 pg/mL, P = 0.830). Men with high-grade cancer had lower levels of serum testosterone than did those with low-grade cancer (3.49 versus 4.09 ng/mL, P = 0.056).

Conclusions

The results of our study have shown that although high-grade prostate cancer is associated with low serum testosterone levels, inhibin does not appear to be the cause of this phenomenon.