Endocrinology of reproduction in the female beagle dog and its significance in mammary gland tumorigenesis.

On the basis of the results of investigations from systemic tolerance tests (and carcinogenicity studies), an attempt is made to evaluate the effects of various progestagens, oestrogens and progestagen-oestrogen combinations on the mammary gland of the dog. The interpretation of such effects in the dog and its relevance in predicting a tumorigenic effect of contraceptive steroids in man is discussed in the light of comparative endocrinology of reproduction. The induction of mammary gland tumours in dogs by certain progestagens or progestagen-oestrogen combinations must be considered as being a species-specific effect, related to the high hormonal potency (progestational activity) of these compounds in the dog and their stimulatory effect on canine growth hormone. Based on the present state of our knowledge and because of the marked interspecies differences of action of contraceptive steroids in dog and man, the steroid-related canine mammary tumours, especially with regard to the doses necessary for contraception, are unlikely to be indicative of a potential hazard to the human female.