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

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.

The use of a 4.7 mg deslorelin slow release implant in male dogs in the field

“…As expected, high testosterone concentrations were more likely associated with a more progressed recovery of spermatogenesis or even restoration in the majority of seminiferous tubules whereas the early time points of castration were associated with an arrest on spermatogonia and spermatocytes as the most developed germ cells. Diff erent to our recent study where fi rst spermatozoa were found 7 to 10 weeks after implant removal in all 6 dogs [ 15 ] , only 2 dogs castrated 10 weeks after removal had fully elongated spermatids in their testis allowing for the assumption that they might have had spermatozoa in ejaculates. In all other dogs except for those that returned earlier, presence of spermatozoa in ejaculates seems unlikely.…”

“…Week ting that the "true" testosterone reference range might be even wider or results might also be dependent on the test used. Samples in this study were run in a RIA that we used repeatedly before, making our results comparable to our earlier studies [5,13,15,16]. Nevertheless, testosterone in TG and CG did not differ significantly.…”

“…Preparation of testicular tissues was as previously described [5,15,16]. Briefly, the testes were cut longitudinally immediately after removal and approximately 0.5 cm 3 parenchyma samples were taken from the area between the tunica albuginea and the mediastinum testis.…”

“…Following an initial short-term stimulation of gonadotropin secretion, sustained exposure to GnRH reduces GnRH-stimulated gonadotropin secretion through GnRH receptor down-regulation, internalization, and signal uncoupling [1][2][3][4]. As a consequence of treatment, testicular endocrine and germinative function is downregulated with basal testosterone concentrations, a significant reduction in testicular and prostatic volume and infertility due to an arrest of spermatogenesis resulting in azoospermia or even aspermia [5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

“…Although the 4.7 mg deslorelin SRI was registered already in 2007 and 2 recent studies described in detail the effects on pituitary-testicular axis and germinative testicular function during 5 months of treatment [16] and subsequent implant removal and recovery of testicular function [15] in 7 male Beagle dogs, but data in larger field populations are still missing in the literature and currently limited to the data from the registration studies [7]. Besides, although confirming the suitability of the 4.7 mg deslorelin-containing SRI as a reversible alternative to surgical castration in general, a considerable variation in terms of onset and duration of effect was identified even in this homogenous Beagle population [15,16]. This clearly supports the need for a larger field study including dogs of different breeds and body weights aiming to the parameters were significantly reduced compared to pre-treatment in the respective dogs.…”