Effect of 19-norandrostenololylaurate on testicular growth in colts.

The effect of anabolic steroid on testicular growth was investigated in 3 experiments. In experiment I, 500 mg of the anabolic steroid was given to 4 colts and 100 mg to another 4 colts, every 3rd week, starting at age 16 months and ending at age 24 months. Six colts served as controls. Both treatments decreased total scrotal width (TSW) within 6 weeks. Seasonal testicular growth during spring partly overcame the effect of steroid treatment. Cessation of anabolic steroid treatment was followed by testicular growth at the same time as TSW in untreated colts was decreasing by virtue of the effect of the season. Four months after the last injection, TSW was smaller in the treated animals than in the untreated animals, but the difference was not statistically significant. In experiment II, steroid was given at a dose of 1 mg/kg every 3rd week to 4 colts and 0.3 mg/kg every week to 4 colts. Six colts served as controls. The animals were 7 months old at the start of treatment and 12 months old at the end of treatment. Treatments decreased testicular widths (TW), within 6-9 weeks. In this experiment, also, cessation of anabolic steroid treatment was followed by testicular growth. Twelve months after the last treatment, TW was smaller in treated than in untreated animals but the difference was not statistically significant. In experiment III, foals were used which were 3 months old at the start and 8 months old at the end of treatment. The steroid was given at a dose of 1 mg/kg every 3rd week to 3 foals. Three foals served as controls. Treatment decreased TW within 6 weeks. Cessation of treatment was followed by a slow testicular growth. Growth similar to that in control animals started after a delay of 4-5 months. TW in treated animals nearly reached TW in controls within 12 months of cessation of treatment.