Anti-Müllerian Hormone as a predictor of resumption of gonadal activity in cats following removal of a deslorelin implant

Anti-Müllerian hormone (AMH) is a dimeric glycoprotein involved in the follicle growth and regulation of the threshold of sensitivity to FSH of preantral and small antral follicles while causing regression of the Müllerian duct during early foetal life and maintain high value until puberty in tomcats. In the adult female, AMH is produced only by the granulosa cells, in adult male AMH is secreted by Sertoli cells. Gonadectomy of mammalian species decreases markedly the serum concentration of AMH which is 100% specific and sensitive for differentiating entire from neutered animals. The aim of this study was to determine AMH serum concentrations in adult cats implanted with 4.7 mg deslorelin implants and to determine the interval between the removal of the implant and the restoration of gonadal activity. Thirty-two privately owned cats (12 males and 20 females) were randomly divided into three different groups that carried a 4.7 mg deslorelin implant for 3, 6 and 9 months. A vaginal cytology smear and reproductive tract ultrasonography were performed on the day of implantation and the day of removal. The same procedure was performed every 7-14 days after removal until penile spikes or first estrus was detected. AMH concentration was determined with an AMH Gen II ELISA microplate kit. All cats showed to have high levels of AMH the day of deslorelin implantation. At the time of removal, AMH concentrations in queens showed to be decreased significantly and they showed an anoestrous vaginal smear; nevertheless, all tomcats display increased AMH concentrations and the absence of any penile spikes. In both tomcats and queens, AMH concentrations suffer a significant inflexion point on the third week after implant removal without differences between implant time treatment. This is the first study that analyses and shows correlations between removal of deslorelin implant and resumption of gonadal activity in adult cats. The length of the treatment showed no influence on gonadal resumption. In queens season seemed to play an important role in oestrus manifestation, showing it at different times even if AMH values were in a normal range weeks before. Moreover, on the day of implant removal, average AMH concentrations was above the threshold reading level (0.01 ng/mL) suggesting that AMH could be used as a method to determine whether a queen has been surgically spayed or chemically neutered.