The Effect of Hypophysectomy upon Mammary Gland Development and Function in the Guinea Pig. ∗

Studies on mammary gland development and lactation during the past few years have indicated that the ovarian hormones are responsible for the proliferation of the glands while the lactogenic hormone of the anterior pituitary is concerned with the initiation and maintenance of milk secretion. However, the possibility of a direct action of the anterior pituitary, as at least a contributing factor in mammary development, cannot be disregarded and obviously requires investigations on the character of development in hypophysectomized animals. Asdell and Seidenstein 1 have reported that hypophysectomized rabbits treated with oestrone and progesterone show mammary development comparable to that obtained in the intact animal. In addition to the question of a direct influence of the hypophysis on mammary growth there are uncertainties in regard to the necessity of the hypophysis for the initiation and maintenance of lactation. 2

Hypophysectomy has been carried out in the guinea pig by a parapharyngeal approach. The operation is well tolerated, operative and early post-operative mortality being low, but deaths, probably due to hypoglycemic crises, are frequent during the first week. This has been successfully combatted to some extent by the routine administration of glucose during the first 10 days after operation. Animals have been maintained for as long as 51 days after hypophysectomy.

Of a group of hypophpsectomized male guinea pigs which were subsequently treated with oestrone† (40 R.U. daily) 6 survived for at least 5 weeks. The character of mammary development as judged by the nipple size, gland spreads, and histological section was of a degree comparable to that observed in normal animals. 3 Autopsy showed pituitary fragments in 2 of these animals.