James H. McDonald

The Rebound Phenomenon of the Spermatogenic Activity of the Human Testis Following the Administration of Testosterone Propionate

The rebound effect of the intramuscular administration of 50 mg test osterone propionate (TP) was studied in 36 oligospermic men. Except for 1 patient who was azoospermic at the start of the study TP produced azoospermia in all patients. 22 of these subjects exhibited a rebound phase after cessation of treatment as evidenced by a striking increase in the number of spermatozoa over pretreatment values. This increase was maintained for 7-45 weeks in 20 of the men. 5 of the 13 subjects who did not exhibit a rebound effect have not returned to pretreatment values. There have since been 5 pregnancies.