Effect of Gonadotrophins on Uterine Growth of Hypophysectomized Mice

Abstract

IT was shown by Lamond and Emmens¹ that the effective dose (ED) of human chorionic gonadotrophin (HCG) for uterine growth in intact immature Swiss albino (S.W. strain) mice was approximately 0.2 I.U. The ED is defined as the amount of gonadotrophin, given in one injection, that will result in uteri weighing approximately 12 mg 44–48 h later (that is, approximate doubling of uterine weight). When the mice were hypophysectomized a few minutes before injection, the ED was increased to about 2.0 I.U. However, 5–6 h after hypophysectomy even very large doses of HCG had no effect on uterine weight. We have shown that the time of the day when the mice are hypophysectomized influences the ED of HCG when the injection is given at the time of hypophysectomy2. The mean ED after hypophysectomy at 9–10 a.m. was 3.0 I.U., and after hypophysectomy at 3–4 p.m. was 0.6 I.U.