Effects of castration on androstenedione, testosterone and dihydrotestosterone plasma levels in adult male rats.

In the present study we investigated the effects of castration on androstenedione (A), testosterone (T) and dihydrotestosterone (DHT) plasma levels in adult male rats 5 and 47 days after castration. In another group of 60-day-old castrated rats, the three steroids have been evaluated during testosterone propionate administration. Our data show that 5 days after orchiectomy all three steroids were significantly decreased (p less than 0.001) with respect to control values. 47 days after orchiectomy, T and DHT were also significantly decreased with respect to the control group. In both groups of orchiectomized rats the A/T ratio increased significantly with respect to controls. On the contrary, the T/DHT ratio sharply decreased. This suggests that DHT, in orchiectomized rats, could derive from precursors other than T. A negative correlation between A and the T/DHT ratio was observed 47 days after castration in adult animals and emphasized upon testosterone propionate administration. In the latter group, T was significantly lower while A is significantly augmented with respect to control values. Finally, the above-mentioned negative correlation indicates a possible prevalent role of A in contributing to the circulating levels of DHT in adult orchiectomized rats.