Presentation Authors: Thomas Masterson*, Miami, FL, Gerwin Westfield, Denver, CO, Nathan Bryson, Ross Ormsby, Mississauga, Canada, Ranjith Ramasamy, Miami, FL
Introduction: Low testosterone (low T) affects around 38.7% of men over the age of 45 and prescriptions to younger men is on the rise. Exogenous long-acting testosterone replacement therapy (TRT) can act as a contraceptive . Very few contemporary studies have evaluated the effect of TRT on gonadotropins and reproduction. Recently, NatestoÂ®, a short acting intranasal gel given three times daily, was demonstrated to increase serum total testosterone while maintaining normal serum levels of gonadotropins. We hypothesized that due to Natestoâ€™s pulsatile (ultradian) systemic exposure, which simulates the pulsatile release of gonadotropin hormones from the HPG axis, it may have lesser effect on gonadotropins than longer acting testosterone gel preparations. We compared the effect of Natesto to a topical testosterone gel on serum FSH, as evidence has shown that FSH is critical for fertility and spermatogenesis
Methods: We performed a post hoc analysis of previously published studies on exogenous testosterone and FSH. Two studies were identified . One prescribing Natesto (11.0mg testosterone/dose, tid), and the other TestimÂ® (50mg, 1% transdermal testosterone). We compared the changes in FSH after 3 months of therapy and in particular attempted to identify characteristics of men who had FSH < 1.5IU/ml as it was considered the lower limit of normal (LLN ). Results are presented as means (SD). Categorical variables were tested for statistical significance
Results: A total of 297 men were prescribed Natesto and 31 hypogonadal men were prescribed Testim (1%). Among the men who were prescribed Natesto, FSH changed from 8.2(11.0) to 5.5 (9.3) after 3 months. A total of 90 (30.3%) men had FSH < 1.5 after 3 months and 39 (12.1%) were â‰¤ 0.5. There were no differences in age or BMI between men who had undetectable FSH and those who did not. Among the 31 men who were prescribed Testim, FSH levels decreased from 6.0 (2.9) at baseline to 2.4 (2.8). Of the 31 men, 13 (41.9%) had FSH below LLN after 3 months.
Conclusions: Testosterone therapy using Natesto increases testosterone while maintaining normal levels of FSH in 70% of men, compared to only 58% in steady state testosterone preparations. Identifying strategies to increase testosterone while simultaneously maintaining reproductive potential is critical for treating young men with low testosterone who wish to preserve fertility.