One study has been conducted in athletes given D-aspartic acid supplementation at a dose of 3g daily for 28 days, and there was a failure to increase testosterone concentrations when measured at 28 days.  This study noted a statistically significant induction of serum D-aspartate oxidase (DAO) which degrades D-aspartate  to a near doubling;  this suggests a possible form of negative feedback, and aromatase (may also be induced by D-aspartic acid  ) was not thought to contribute due to estrogen being unchanged.
The second clinical trial (Trial 2) was a 12-week randomized, double-blind and placebo-controlled trial that enrolled 558 generally healthy postmenopausal women between 40 to 80 years of age (mean years) who, at baseline, had identified moderate to severe dyspareunia as their most bothersome symptom of vulvar and vaginal atrophy. In addition to dyspareunia, women had ≤ 5% superficial cells on vaginal smear and a vaginal pH > 5. Women were randomized in a 2:1 ratio to receive once daily vaginal insert containing mg INTRAROSA (n=376) or placebo (n=182). The primary endpoints and study conduct were the same or similar to those in Trial 1.