Association of androgen receptor signaling in human corpus cavernosum with serum testosterone levels

Abstract Introduction Testosterone (T) plays an important role in properly developing and maintaining male reproductive tissues. The normal serum testosterone levels can vary between 300 to 1000 ng/dL or 10.4 to 34.7 nmol/L. However, it is unclear whether androgen receptor signaling can vary based on serum T levels or the half-life of testosterone therapy. What remains unknown is whether there is a uniform serum T level above which androgen receptor signaling within the tissue remains similar (saturation hypothesis). Objective We first evaluated whether varying serum levels of T alter androgen receptor (AR) signaling in human penile tissue. Then, we evaluated and compared AR signaling in corpus cavernosum tissue of men treated with short-acting vs. long-acting testosterone. We hypothesized that we would find similar AR signaling in the penile tissue of both eugonadal and hypogonadal men as well as those men receiving short and long-acting testosterone. Methods We obtained human corpus cavernosum (hCC) tissue biopsies during penile surgery (for erectile dysfunction) from 14 men. We recorded their serum T levels on week prior to surgery before 10AM. We used western blot to evaluate adrenergic receptor (AR) and VEGF protein levels. Men without erectile dysfunction undergoing penile surgery for Peyronie's disease were used as controls. Results The median age of participants was 61 (IQR 12) and the median T level was 325ng/dL (IQR 201.45). The results of western blot showed expression of similar levels of VEGF in hCC samples from men with T >200ng/dL. However, men with serum T levels lower than 200 ng/dL had decreased expression of VEGF and AR. Conclusions This finding is significant because it demonstrates that serum testosterone beyond a certain threshold may have a minimal impact on erectile function. If a serum testosterone threshold is identified, this threshold could be a valuable target for future studies on the effects of testosterone on ED. It may alter the treatment threshold for men who have ED as their primary symptom of hypogonadism. This data also suggests the saturation value for penile androgen receptors. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Acerus Pharmaceuticals, Boston Scientific, Coloplast, Endo Pharmaceuticals, Empower Pharmacy, Nestle Health, Olympus, Hims, Inc