Postponement of canine puberty by neonatal administration of a long term release GnRH superagonist

The objective of this study was to assess the efficiency and clinical safety of postnatal administration of a GnRH agonist on canine puberty postponement. Sexual steroids and histological gonadal changes were also described. Twenty-four littermate puppies were randomly assigned to: Deslorelin acetate 18.8 mg sc (DESLO; n = 12) or Placebo: sc (PLACE; n = 12) postnatally. The dogs were clinically and endocrinologically followed up until puberty when they were gonadectomized and their gonads histomorphometrically studied. Deslorelin postponed the age of puberty (72.7 ± 4.8 vs. 35.8 ± 1.9 weeks; P < 0.01) in these dogs. At the time of this submission, 3 DESLO dogs (108 weeks old) remain non-pubertal. All dogs concluded growing at a similar age (29.75 ± 2.44 vs. 29.25 ± 0.90 weeks; P > 0.1) independently of their group and pubertal status. None of the females had side effects while the 2 non pubertal DESLO males presented bilateral cryptorchydism. All the bitches ovulated at puberty (P > 0.1) and the 2 DESLO that were mated became pregnant. Deslorelin postponed basal serum sexual steroids up to puberty in both genders (P < 0.01). The histomorphometrical study of the testes revealed that the tubular diameter (P < 0.05), germinal epithelium height and composition (P < 0.01) were decreased in DESLO group. Ovarian structures did not differ between treatments (P > 0.05). It was concluded that postnatal deslorelin decreased sexual steroids reversibly postponing puberty in both genders without side effects in bitches and causing 2/6 of cryptorchydism and impairment of testicular histomorphometry in male dogs.