STUDIES ON THE VALIDITY OF THE HOOKERFORBES TEST FOR THE DETERMINATION OF PROGESTERONE IN UNTREATED BLOOD*

Abstract

The simultaneous, intrauterine injn. of certain estrogenic steroids and progesterone prevented the action of the latter hormone on the stromal nuclei of the uterus of the mouse (Hooker-Forbes test). Estradiol blocked the test at a ratio 1:20 parts of progesterone, estrone blocked at a ratio of 1:1 and estriol failed to block at a ratio of 20:1. Blocking action of the estrogens depended on ratio of estrogen to progesterone, not on the absolute amt. of the former. Analysis of blood estrogen and progesterone showed that there was an insufficient amt. of estrogen present to interfere with the assay of progesterone and that under normal physiologic conditions the Hooker-Forbes test was valid for the detn. of progesterone in untreated blood. Tests involving both pregnanediol and testosterone failed to reveal any antagonism to progesterone. This study also confirmed the observation of Hooker and Forbes that this test can detect a concn. of 0.3 [mu]g./ml. of progesterone.