Deslorelin implants in pre-pubertal female dogs: short- and long-term effects on the genital tract

Deslorelin acetate is a GnRH agonist used for contraception in dogs. This study aimed to evaluate the treatment of pre-pubertal female dogs with deslorelin acetate implants, to better investigate the primary stimulatory effect of the drug and the long-term effects on the genital tract, throughout repeated treatments. Sicilian hound female dogs (24) were randomly assigned to treated group, control group 1 and control group 2. First group bitches were implanted at 4.5, 9.0 and 13.5 months and monitored clinically, ultrasonographically and endocrinologically, throughout the study period (13.5 months). Control group 1 bitches were not implanted and clinically monitored for the same period. At 18 months, the animals underwent ovariohysterectomy, thus allowing evaluation of the internal genitalia. Control group 2 bitches were ovariohysterectomized at the age of 4.5 months. The suppression of oestrus was obtained in the treated group despite the fact that the first implant caused a modest increase in plasmatic levels of 17-beta estradiol and an evident cornification of the vaginal mucosa cells (50-80%). Estradiol and progesterone were at baseline levels for the remaining study period, in which no other oestrous manifestations were observed. The external genitalia maintained a juvenile appearance. The ovaries, ultrasonographically, showed no follicular structures and stayed the same size. At 18 months, the genital tract was still juvenile with inactive small ovaries and a thin filiform uterus. Deslorelin suppressed ovarian activity in pre-pubertal bitches, and oestrous induction was not observed despite the presence of the primary stimulatory effect of the drug. Juvenile genitalia were an expected side effect of the treatment.