Comparison of Intratesticular Testosterone between Men Receiving Nasal, Intramuscular, and Subcutaneous Pellet Testosterone Therapy: Evaluation of Data from Two Single-Center Randomized Clinical Trials

Purpose: Testosterone replacement therapy (TRT) can potentially cause decreased spermatogenesis and subsequent infertility. Recent studies have suggested that 17-hydroxyprogesterone (17-OHP) is a reliable surrogate for intratesticular testosterone (ITT) that is essential for spermatogenesis. We evaluated data from two ongoing open-label, randomized, two-arm clinical trials amongst different treatment preparations (Trial I) subcutaneous testosterone pellets (TP) and (Trial II) intranasal testosterone (NT) or intramuscular testosterone cypionate (TC). Materials and Methods: Seventy-five symptomatic hypogonadal men (2 serum testosterone <300 ng/dL) were randomized into open label randomized clinical trials. Eligible subjects received 800 mg TP, 11 mg TID NT or 200 mg x2 weeks TC. 17-OHP and Serum testosterone were evaluated at baseline and follow-up. The primary outcome was changes in 17-OHP. Secondary outcome was changes in serum testosterone. Data was analyzed by two-sample and single-sample t-tests, and determination of equal or unequal variances was computed using F-tests. Results: Median participant age was 45 years old, with overall baseline 17-OHP of 46 and serum testosterone of 223.5 ng/dL. 17-OHP significantly decreased in subjects prescribed long-acting TP or TC. The 4-month change in 17-OHP in the NT group (-33.3% from baseline) was less than the change seen in TC (-65.3% from baseline) or TP (-44% from baseline) (p=0.005). All testosterone formulations increased serum testosterone levels at follow-up, with the largest increase seen in TC (+157.6%), followed by NT (+114.3%) and TP (+79.6%) (p=0.005). Conclusions: Short-acting nasal testosterone appear to have no impact on serum 17-OHP especially in comparison to long-acting testosterone formulations. All modalities saw significant increases in serum testosterone levels at follow-up. NT and other short acting testosterone formulations may better preserve ITT and be beneficial for hypogonadal men seeking to maintain fertility potential while on TRT.