What Happens in Male Dogs after Treatment with a 4.7 mg Deslorelin Implant? II. Recovery of Testicular Function after Implant Removal

SIMPLE SUMMARY: Although widely used in clinical practice as an alternative to surgical castration, the recovery of testicular endocrine and germinative function subsequent to treatment with a 4.7 mg deslorelin implant has not been well characterized until now. It is, however, relevant for the veterinary practitioner to advise the pet owner about the expected return to “normal” testosterone concentrations, prostatic volume, and pre-treatment semen quality. Our study showed that testosterone was no longer different from untreated controls on D14 after implant removal, whereas normospermia was reached on D84-133. All of the effects induced were fully reversible, albeit after individually varying time periods. ABSTRACT: Although deslorelin slow-release implants are widely used in the clinic, detailed published information about the recovery of testosterone concentrations (T), semen quality, and testicular and prostatic volume (TV, PV) after treatment is still missing. This article aims to characterize changes during restart after a five-months treatment and subsequent implant removal. Seven male Beagle dogs were treated with deslorelin (treatment group, TG), and three saline-treated dogs served as controls (CG). Deslorelin implants were removed after five months (D ex), followed by detailed andrological examinations for TV, PV, semen collection, and blood sampling for T-analysis with/without GnRH/hCG stimulation tests. TV, PV, and T increased rapidly after D ex in TG, not differing from CG from D91 (TV), D49 (PV), and D14 (T). The first sperm-containing ejaculates were collected between D49 and 70, whereas the samples were normospermic between D84 and 133. A T increase (>0.1 ng/mL) subsequent to the GnRH/hCG stimulation test was observed from D28/29 onwards, respectively. Histological assessment of testicular tissue at the end of the observational period (D149 after implant removal) revealed normal spermatogenesis. Our data confirm that the restart of endocrine and germinative testicular function is highly variable, but nevertheless, all of the effects induced were reversible.