Premature gonadal failure in female dogs and cats.

Premature gonadal failure has been detected in phenotypically female dogs and cats with defective prenatal germ cell migration (ovarian aplasia), defective prenatal differentiation of the gonadal ridge into ovarian tissue (true hermaphroditism, male pseudohermaphroditism, ovarian dysgenesis in the presence of XO or XXX sex chromosome complements) or defective gamete maturation in the presence of primordial ovarian follicles (lymphocytic oophoritis, thyroid insufficiency). The most common of these is defective gonadal differentiation in animals with true hermaphroditism and failure of gamete maturation in thyroid insufficiency. A common clinical sign of premature gonadal failure in companion animals is failure to show a pubertal oestrus by 2 years of age. Diagnostic evaluation of such animals should include determination of the karyotype, plasma concentrations of LH and FSH and of thyroid hormones, gonadal histology, and gross evaluation of the Müllerian duct system at laparotomy.