Concerning the effect of D-Asp on the induction of testosterone release, after 12 days of D-Asp treatment, the levels of testosterone in the serum of the participants were significantly increased compared with basal levels. Out of 23 participants, 20 had increased testosterone. From a mean of 4.5 ± 0.6 ng/ml serum at zero time, it rose to 6.4 ± 0.8 ng/ml, a 42% increase (Table 1). Statistical analyses indicated a significant effect [ANOVA with repeated measures: treatment effect: F(1,82) = 7.724, p < 0.0082] and a significant interaction between treatment and days [F(2,82) = 32.599; P < 0.0001]. As with LH, so also with testosterone, the effect of D-aspartate was time dependent. When subjects were treated with sodium-D-aspartate for only 6 days, testosterone was found of 1.15-fold higher than basal levels, but this increase was not statistically significant (Table 1). Interestingly 3 days after the suspension of D-Asp treatment, testosterone was still increased 1.22-fold compared with the basal levels (5.8 ± 0.6 ng/ml against 4.5 ± 0.6 ng/ml). Fisher's post-hoc analysis also revealed a significant difference in the testosterone concentration in the serum 3 days after the end of the treatment (p < 0.01) (Table 1). One plausible explanation of this phenomenon is that since in rats ingested D-Asp remains accumulated in the testes in significant amounts until 3 days after the suspension of D-Asp treatment (see below), if it is assumed that in humans D-Asp also remains significantly increased in the testes 3 days after the suspension of D-Asp treatment, we can deduce that in humans as in rats, D-Asp had remained accumulated in significant amounts in the testes and consequently it continued to stimulate testosterone release.