[Impact of hypothyroidism on bitch fertility and neonatal mortality and morbidity - a review of the literature].

Abstract

There are a few studies and case reports that postulate a connection between hypothyroidism and reproductive disorders in bitches and an increased neonatal mortality and morbidity in puppies. Other studies, however, cannot demonstrate a connection between hypothyroidism and reproductive disorders in bitches. In this work, the relevant literature is to be checked for its evidence. The connection between hypothyroidism and reproductive disorders in the bitch, puppy mortality and neonatal morbidity to hypothyroidism will be analyzed based on a literature review. For this purpose, the available German and international "English-language" literature from 1986 to January 2023 was analyzed. It turns out that only a small amount of literature contains high levels of scientific evidence, as it mostly consists of case reports and expert opinions. In some case reports a connection between estrous abnormalities, galactorrhoea and infertility and the presence of hypothyroidism could be seen, but in experimental studies and according to the opinion of other authors the connection between hypothyroidism and reproductive disorders does not exist. A negative influence of hypothyroidism on the birth process could not be clearly proven. In an experimental study, although the duration and intensity of uterine contractions were longer and weaker in animals with hypothyroidism, the interval between pup births was not affected. Only in the area of neonatal mortality and morbidity a connection with the hypothyroidism of the dam could be demonstrated. The puppies of affected bitches showed a lower birth weight and were weaker than puppies of euthyroid bitches. The importance of hypothyroidism for fertility in the bitch has not yet been documented in the literature, but this endocrinopathy seems to have an influence on neonatal vitality.