Anti-Müllerian Hormone Concentrations for Determining Resumption of Sertoli Cell Function following Removal of a 4.7 mg Deslorelin Implant in Tomcats

SIMPLE SUMMARY: The anti-Müllerian hormone is considered the gold standard biomarker for Sertoli cell function evaluation. In male fetuses, Sertoli cells secrete high concentrations of AMH in order to suppress the development of the Müllerian ducts. This secretion is significatively reduced after puberty by the action of the follicle-stimulating hormone. Agonists of the gonadotropin-releasing hormone (GnRH) bind to GnRH receptors in the anterior hypophysis, causing an initial stimulation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release until a desensibilization of the receptors occurs. In tomcats, testosterone concentrations tend to be basal (below 0.1 ng/mL) 20 days after the application of a 4.7 mg deslorelin implant with an average length of 18 ± 3 months. All the effects caused by the effect of the deslorelin molecule are completely reversible after the implant activity or after its removal. The present study shows that AMH concentrations increased from 20.95 ± 4.97 ng/mL to 82.41 ± 14.59 ng/mL and decreased to 28.42 ± 7.98 ng/mL three weeks after removal of a 4.7 mg deslorelin implant. Achieving pre-treatment AMH concentrations 3 weeks after removal of the implant can be considered Sertoli cell activity resumption. ABSTRACT: Background: Deslorelin implant use in cats is a medical alternative to surgical sterilization, and due to its prolonged efficacy, its use has shown growing interest in the veterinary community. In the case of breeding facilities, its removal is often requested for the early restoration of testicular function. As anti-Müllerian hormones (AMH) in males is dependent of testosterone secretion, its assay may determine the restoration of testicular steroid secretion. An average of 3 weeks has been already described for tomcats’ testicular function resumption after implant removal, but information about AMH concentrations in deslorelin-treated tomcats is lacking. Methods: Fourteen tomcats were treated for temporary suppression of fertility with a 4.7 mg deslorelin implant, which was surgically removed after 3, 6 or 9 months (n = 6, 4 and 4 tomcats, respectively). A general clinical and reproductive check with a gonadorelin stimulation test for testosterone determination was performed before deslorelin implant administration. After implant removal, tomcats’ testicles were ultrasonographically checked for volume determination every 1-2 weeks with observation of the glans penis (presence or absence of spikes) and blood collection to assay both testosterone and AMH concentrations. Results: AMH concentrations increased significantly during the deslorelin treatment from 20.95 ± 4.97 ng/mL to 82.41 ± 14.59 ng/mL (p < 0.05). Following implant removal, AMH concentrations progressively decreased to pre-treatment levels, with a value of 28.42 ± 7.98 ng/mL on the third week post-removal where testosterone secretion was again detected. Conclusions: Even if a big variability of AMH concentrations exists between male individuals, resumption of tomcats’ testicular function following a deslorelin treatment can be determined by AMH assay.