Relation of Estrogen to Ossification and the Levels of Serum Calcium and Lipoid in the English Sparrow, Passer Domesticus *

Skeletal hyperossification follows the injection of estrogen into mice1 and pigeons.5 In the female sparrow similar hyperossification occurs normally during the egg-laying season or if the ovary is stimulated to full activity by gonadotropic hormones during the non-breeding season.2 Attempts to duplicate this by the injection of estrogens have failed.2 Observations on chickens3 7 and on ducks4 indicate that either a higher dose of estrogen or a longer period of treatment might be necessary in order to bring about the osseous changes in the sparrow. In addition, the fact that the sparrow ovary produces appreciable amounts of male hormone suggested that this hormone might play some role in the laying down of bone within the marrow cavities. The present experiments were undertaken in order to test these possibilities. Since in other birds calcium and lipoid metabolism undergoes extreme alteration under the influence of estrogens,3 4, 8 this phase of the problem has also been investigated in the sparrow.