To investigate the effects of androgen administration at different periods of prepubertal life on penile size and potential fertility in hormonally normal rats.

Eighty Sprague-Dawley rats were divided into 4 groups; group 1 received weekly injections of testosterone enanthate (8 mg/100 g) at 1-3 weeks group 2 at 3-5 weeks, group 3 at 1-5 weeks, and group 4 was control (n = 20 each). Animals were killed at age 60 days. Penile length, penile, testicular, and epididymal weight, testicular fertility index, serum follicular stimulating hormone, luteinizing hormone, and testosterone levels were measured and quantitative real time polymerase chain reaction of penile androgen receptor messenger ribonucleic acids was performed.

Penile length in the 3-5-week injection group was significantly longer than controls (41.18 vs 39.13 mm, P = .011), and it was smaller than controls in the 1-3 week injection group (37.24 vs 39.13 mm, P = .020). The penile wet weight showed a similar pattern to stretched penile length; however, statistical significance was not found. Testicular weight was significantly less in the testosterone injection group than controls (1.79, 2.16, 2.24, and 2.78 g in groups 1-4, respectively) as well as the epididymal weight (0.48, 0.42, 0.59, and 0.69 in groups 1-4, respectively). The mean tubular diameter and germ cell count were significantly reduced in the testosterone treated group. Total penile androgen receptor messenger ribonucleic acid level was significantly lower in group 3 as compared with controls.

Testosterone administered during early prepubertal life resulted in smaller penis than controls, as well as having an adverse effect on testicular development which can jeopardize potential fertility.