TROPHIC HORMONES OF THE PLACENTA: FAILURE TO DEMONSTRATE THYROTROPHIN OR ADRENOCORTICOTROPHIN PRODUCTION IN THE HYPOPHYSECTOMIZED PREGNANT RAT1

It has been known since the work of such investigators as Allan and Wiles (1932) using the cat and Pencharz and Long (1933) using the rat that pregnancy can continue in gravid animals after hypophysectomy. This observation has been confirmed in many different species such as guinea pigs, mice, dogs, rabbits, and monkeys. It is now well-established, of course, that pregnancy is able to continue because the placenta takes over in part the functions of the pituitary gland and ovary. In the lower mammals investigated, the placental hormone chiefly responsible for maintaining pregnancy seems to be a luteotrophin, since ovariectomy in animals such as the rat results in abortion or resorption of the foetuses in hypophysectomized pregnant animals although pregnancy continues undisturbed if the ovaries are left intact. In certain species including the primates, the placenta is able also to take over the function of the ovaries