INHIBITION OF MAMMARY GROWTH BY LARGE AMOUNTS OF ESTROGEN1

Abstract

The mammary glands of o mice given weekly injs. of 50[gamma] of estradiol benzoate and estradiol dipropionate were smaller than those of mice receiving smaller doses. The inhibition of mammary growth was nearly complete in mice receiving 50[gamma] of estradiol dipropionate. A similar inhibition of the mammary glands of immature or young [female] monkeys and one [male] monkey was noted when over 400y estradiol benzoate were injected weekly for prolonged periods. The mammary glands of 4 young [female] dogs receiving weekly doses of 133 to 533[gamma] of estradiol benzoate for long periods and later, in 3 animals, larger doses for brief periods showed no or little growth. During the same period the mammary glands of a virgin control dog underwent extensive development. In [male] mice of the C3H strain, in which the [female][female] are susceptible to mammary tumors, the highest incidence of mammary tumors in the estrogen-treated [male] mice occurred in the group receiving doses permitting the more extensive mammary growth.